We use labels to reduce large concepts to single reference points. When you argue about what a label represents, you're essentially arguing about the right way to organize the concepts. This is usually a waste of time as, at the heart, what we're usually more interested in the concepts represented by the labels more than the labels themselves.
In other words - stop worrying about whether you like the OP's definitions. You can note you think of it differently, but use them as references for the discussion and move on.
Most of my campaigns of D&D would fall in the area the OP has trouble distinguishing: Advanced Linear Adventure and Basic Sandbox Adventure. They essentially follow the 'Babylon 5' model as I like to call it.
Babylon 5 was the first American multi-season Sci-fi show that carried concepts from episode to episode and season to season as a core mechanic of the storytelling. You had episodic stories that wrapped up in a single episode, multi-episode arcs, season arcs, and multi-season arcs ... and they wove together to create the entire epic tale. That is what I strive to do.
When I start with a new group I run one campaign. I have run it many times since the 1980s when it was first created. It has dated elements.
It begins with the PCs being fledgling adventurers in a small walled Kingdom. They go on a typical low level "investigate this ruin" type adventure after being hired by someone that turns out to be working for the Royal Family. At the end of this 2 session dungeon all heck breaks lose. With only a few very vague foreshadowing bits hinting that something is up, a veritable army of monstrous humanoids and monstrosities attack the Kingdom. The invading force is far, far, far, far more powerful than the combined resources of the small walled Kingdom. I consider everything up to this point to be railroaded for the PCs. I give them one solid hook and expect them to take it.
At this point, the PCs hit a sandbox situation. They get a number of hooks: 1.) People are fleeing and need time to escape. The PCs can try to slow down the invading army. 2.) The Princess of the Kingdom disappeared right before the assault took place. Due to their involvement in that first adventure, the PCs are in a position to locate her. Someone asks if they are willing to do this. 3.) There are people trying to figure out why the invaders attacked. The PCs have a vested interest in figuring this out. 4.) Every sign indicates that no matter what, the invaders are too powerful to stop and people need to flee across the seas. Do the PCs go? 5.) A resistance organization forms quickly amongst those unable to flee and the PCs may get a chance to join if they do not flee.
Additionally, PCs might decide to loot, or use the opportunity to murderhobo through the enemy forces as much as they can.
As a DM, I prepare for the PCs to stay in the region or go across the seas to the "new land" where the heroes may try to help the refugees establish a new place to live with the constant threats of the new realm and the invaders following them around. I also prepare for that to unfold without them present while the PCs stay in the old lands. Either way, I consider this the "first Babylon 5 season". If you've watched Babylon 5, you may remember that there is a primary storyline for the show - and we only sniff hints of it during the storylines of the first season. That is true here. I drop foreshadowing hints about the main storyline through these first adventures ... but around the time the PCs reach level 5, those hints start to coalesce into threads and the PCs realize they are in a position to play a central role in an unfolding storyline.
Levels 5 to 11 involve adventures that add more understanding for the PCs. Using Babylon 5 as a reference, as sessions go by they learn more about the Shadows and Vorlons - and other First Ones / Elder Beings. They're gathering the puzzle pieces but do not have enough to see the big picture for a bit. There is no "big reveal". There is a constant swirl of information that is revealed and re-revealed (as players forget or miss significance) over time until one of them says, "Hey, do you think ...." and there is a collective realization of what is going on. This could happen very quickly (like level 6) or take a longer time (like level 11), but once it does the PCs will see the game board differently. They'll realize that certain situations they've ignored are meaningful. They'll realize that they have played a huge role in the fate of the entire setting. They'll realize that they have the MacGuffin that is at the core of the entire threat ... or that they did before they lost it a year back. Regardless, as they advance to that level where they can teleport, use divinations to get answers, and otherwise 'break the rules' that ground low level games they are in a position to adventure across the planes and try to deal with the threat.
There are a lot of ways that levels 5 to 17 can unfold. It is a huge sandbox of options where certain clues can be acquired. The threads that interest them most can be followed and information can be gathered about the rest through hearing news, using magic or through the natural interests of NPCs associated with some of those other storylines being interests that focus on the PCs due to their actions.
In the end, as they go from that point of realization the campaign goes through reductions and narrowing. Storylines resolve and influence the available options. As with Baldur's Gate 3 - something you decided to do in the Druid Grove in Chapter 1 may change what options you have in Baldur's Gate in Chapter 3. At that point, there is a big reveal. It is the twist or pivot around which the campaign resolves. Everything they've done so far is balanced against that pivot point and determines what options they can pursue. It is important to know that this pivot point was inevitable. Everything that mandated it would happen occurred outside the reach of the PCs. The pivot is going to happen - but what pivots around it is determined by the PCs. A wall was always crumbling and was always going to break ... the PCs are just determining what is on both sides of the wall as they go through the campaign.
Then they engage in the ENDGAME in which they decide how my campaign setting will go forward. So as not to reveal too much, the Babylon 5 equivalent would be: Do they aid the Shadows to cast off the Vorlon manipulations? Do they aid the Vorlons to put a threat to the destructive chaos of the Shadows? Do they try to stop the warfare between them? Or do they figure out how to conquer all of them using the tools they've gathered? They could also just decide to let it unfold without them as they focus on personal interests ... although I have not seen that happen yet.
When the campaign ends I hold a Q&A. I let the players ask anything. I start it by telling them of the Babylon 5 structure and then explaining how the puzzle pieces fit - especially the ones they did not explore. In all the time I've run this, there is one story hook that nobody ever touches - and I think it is really, really, really cool. I intentionally try to hype it up as I want the players to have freedom and write their own fates ... but when I describe it to the players they usually agree that they wish they'd taken the hook. Regardless, after the Q&A, the PCs are retired and the next campaign takes place in a version of my world that is heavily influenced by the results of the first campaign.
In my eyes, This is a railroad sandwich. I start with a linear story, explode into a sandbox, and then dig through the sandbox to reveal rails that bring them eventually back to a railroad event. From there, they're back on a railroad ... but they selected where the rails go.
I see this structure all over BG3. If you go to the end of the campaign there is a single resolution point. What options you have at that point are determined by everything you've done to reach that point. While the core elements of the end may be very similar for a Chaotic Evil Dark Urge and a Lawful Good Light Cleric ... the way it unfolds are hugely different - and you may make decisions that result in VERY different scenarios for the Sword Coast (or all planes). The same is true of this campaign.
The next campaign I run is usually my megadungeon. The PCs are helping an exploratory team secure a ruined village as a trading port along a trading route that has returned to relevance. Goin in, the players know this is a megadungeon campaign. They discover a huge manor house on the hill overlooking the village that is being reestablished and get a chance to explore it - and the dungeon beneath it - and the feywild, shadowfell, and ethereal reflections of it. They also discover all the extraplanar connections in it that take them to distant lands, to distant planes, and to distant lands. There is no 'big storyline' here - but instead a vast number of shorter mysteries that all interconnect a bit, but not in a way that heads towards a single resolution. As they advance in power the PCs can "unlock" additional parts of the megadungeon - allowing their advancing abilities to be the gatekeepers on the more difficult areas. It is akin to the megadungeon Matt Mercer added to campaign 2 of Critical Role - but with several hundred encounter options. This is an entirely different structure than the first campaign - but players have responded equally favorably to both.