What is the everything else?
Everything else is everything, Attack, AC, HPs, Damage, Powers, Everything. You dont have a minion Ogre because in the fiction you have a Ogre that only has 1 HP. You have a minion Ogre because the game mechanics need to add extra XP to balance the fight.
Level is a mechanical device. It informs the referee about appropriate mechanics to use, via the monster/NPC-building rules and the DC-by-level chart.
Exactly you dont run around trying to defend Level as some kind of fictional narrative, or AC as some kind of fictional narrative. Why does a level 8 Ogre have a different AC then a level 11 Ogre? Because level 11 monsters have higher ACs then level 8 monsters.
Tier of play is a notion about fiction, and that informs what the fiction is. And we choose fiction first, then mechanics.
Except we dont. By choosing a tier of play we have already chosen the mechanics. Heroic tier levels 1 to 10, Paragon 11 to 20. Its all mechanics first.
First, the fiction: I shove my hands into the forge to hold down the hammer so the artificers can work it. Then, the mechanics: The DC for that Endurance check is such-and-such.
Except that first the mechanics of a skill challenge require the PC to use his best skills. So first the mechanics high Endurance and second the fiction shove my hands into the forge and hope the DM rolls with it.
First the fiction: The dwarf who can hold down hammers in furnaces comes across a hobgoblin phalanx. Then, the mechanics: That phalanx is a 16th level gargantuan swarm.
First the mechanics, at the Dwarfs level he needs to face a creature of at least level 16, then the fiction its a hobgoblin swarm.
What if he is even higher level then its a level 21 swarm of I dont know Dire hobgoblins or oh yeah Vrocks. Yeah Vrocks sound like a level 21 swarm.
The reason an ogre is a standard for 8th level PCs and a minion for mid-paragon ones is because the mechanics follow the fiction.
No, as I have already shown you need a minion for mid-paragon players so you just call it an Ogre. If it really was fiction first then the Ogre that mid-paragon players were fighting would still be the Ogre that 8th level players were fighting. That is how fiction works, its not some kind of Schrodinger Ogre that only coalesces into its final form when you open the box and reveal what level you are. We already have that creature, it is a Boggart.
No one in this thread has given a consistent account of how DC-setting works in 5e, as far as the relation between fiction and mechanics is concerned.
But as far as I can tell it is mechanics first: we don't have a prior, in-fiction conception of how tough a 15th level fighter is, and then set DCs and stat up creatures that respond to that. We don't know how tough a 15th level fighter is until we see what s/he can do, taking certain mechanics published in the MM as given.
That's not fiction-first. It's mechanics first.
As far as I am aware the DCs in 5e dont change just because the PCs have leveled up. You are not always needing to roll a 12 to open a lock at every level because this lock is a slightly stronger lock then last level.
How do you determine a DC in 4e? Simple fiction first. Oh wait no, you look up the level chart that tells you the DC. Just like when you are doing your skill challenges.