But doesn't the level system work against you here?
No.
You can have all the locations and whatnot that you want, but, there are practical limits on what a 1st level party can do.
No more than what a party of 50-point GURPS characters can do.
In my Majestic Fantasy RPG, here’s how I handle this, from page 67 of the Basic Rules:
Experience
A character’s Class Level is representative of the character’s life experience. In general, all characters have a class and level. In some cases, hit dice and notes on special abilities may act as a shorthand when the full details of class and level are not needed.
Levels 1 to 2 are considered to be trained apprentices. Characters are nominally capable of doing the job of their class or profession, but still have more to learn before being considered a veteran or fully trained.
Level 3 is where characters are considered professionals within their class or profession. In a guild, this is the point where a character becomes a journeyman and is allowed to take employment with any master willing to hire them. Burglars will now be respected enough to run their own heists. Clerics become full priests of their religion, allowed to officiate at services and ceremonies. Fighters receive their first minor command. Finally, Magic-Users are considered fully trained and ready to make their own way in the world.
Level 6 is where characters are considered to have mastered their profession and ready to assume various leadership roles. In guilds, the character would be considered a master of their profession. Burglars gain control over the jobs and heists done in a neighborhood. A Cleric becomes eligible to be a bishop, responsible for the flock of a small region or city. Fighters start to independently command troops as a captain. Finally, Magic-Users start to take on apprentices to train and to assist them in their expanding array of research.
Level 9 is where the character reaches the pinnacle of their profession and occupies the highest leadership positions. In guilds, the character becomes a grandmaster, either leading the guild or with a place on the council, setting policy for the guild. Clerics become High Priests or Archbishops in charge of their religion’s hierarchy for a region or realm. A Fighter would be promoted to general or granted lands to rule as the lord or lady of the land. Finally, a Magic-User would be known as a full wizard and widely respected for their knowledge and skill. They would attract many apprentices and fellow Magic-Users to learn and assist the wizard in their research.
At level 12, the character is considered a paragon of their profession, somebody whose skill and exploits are worthy of being used as an example for others to follow. In modern times, these characters would win the Nobel Prize or be Olympic-caliber athletes.
At level 16, the character becomes more than a paragon and moves into legendary status. Their deeds are famous through the continent or even the world. Consider these on par with our own world’s Alexander the Great, Julius Caesar, Sun Tzu, Plato, or Aristotle.
Which means that your sandbox locations have to be to some degree, constrained by that fact. You can't put 1st level characters into Queen of the Demonweb Pits. Well, you can, but, only for a really short time.
A better comparison is a group starting in the City State of the Invincible Overlord, who are aware of the Forest of Dearthwood, once the elven kingdom of Silverwood, now an orc-infested wilderness.
City-State is located in the lower left corner (the red dot).
The reality of Dearthwood:
If a party of 1st-level characters (or 50-point GURPS characters) decides to enter Dearthwood “just because,” their chance of dying is high. But if they treat themselves as beginners, do their research, and seek out help or intelligence, they may uncover something within reach, like the
ruins of an Elf Lord’s temple. That’s where opportunity lies.
As I mentioned earlier, everything in my setting creates ripples. I put a great deal of effort into making the world plausible, even within a fantastical framework. I don’t wave it away with “it’s fantasy”, I follow the implications. One of those is that, even in a dangerous world, there are always opportunities for the inexperienced to find adventure and wealth. Like anything else, adventuring develops a culture around it, one that novice adventurers can learn from, tap into, and use to discover opportunities appropriate to their capabilities.
A common criticism of this approach is: “Why bother? I only have so much time, just skip to the good stuff.” Or “I feel like I’m playing Mother May I or playing Twenty Questions.” My response is that getting to the good stuff is part of the fun. And it isn’t handled through dry procedures or filling out spreadsheets, as classic roleplaying is often depicted; it happens through interacting with NPCs, through roleplaying, and through interacting with the World in Motion and NPCs' personalities. The process of navigating that, matching your character’s goals to the agendas of others, uncovering information, and making decisions in uncertain circumstances, is what makes the journey as compelling as the destination.
And, as well, the players are also cognizant of these limitations. They know that at Level X, they can, with some degree of accuracy, predict which adventures are in their wheelhouse. And, since none of us particularly want to TPK the players, there's going to be some pretty serious signposting going on if the players choose to wander into somewhere that is way above their weight class.
It works a lot like mountaineering. Novices don’t tackle Everest first; they train, plan, learn, and practice on mountains more suited to their skill levels. Or better yet, consider deep cave exploration, where dangers are real and not always obvious. Inexperienced cavers will tackle easier, more shallow caves first before tackling more difficult ones. Preparation is key; it is no different with adventuring.
Plus, one thing that leaps out at me when reading the accounts of mountaineers and cavers is not just the technical elements of their craft, but the stories of the people they interact with. Many mock this as unnecessary drama, but to me, it makes everything they write about more human and relatable. For a tabletop roleplaying campaign, it is an invaluable resource for elevating something that would otherwise come across as a dry and technical series of procedures into a deeply engaging experience.
This is the point I've kept trying to make all throughout this thread. The D&D system itself is going to seriously constrain any sandbox. It's unavoidable.
My experience says otherwise. And I’m still in the process of documenting that experience, so I understand the skepticism.
The system only constrains a sandbox if you treat level as a script; if you treat it as an indication of life experience, then it's just one more part of how players make informed choices in a dynamic world.