Will I have the opportunity to 100% Metroid Dread before the final boss if I missed things?

Solution 1:

Yes, nothing in the game is missable, at least until you defeat the final boss.

If you're fighting the Chozo Soldier in Artaria, that means ZDR is currently frozen. At this point, you won't be able to explore the map much, because almost every door will be frozen shut.

Once you defeat the next boss in Cataris, ZDR should return to normal, and you'll be able to explore freely once more.

However, you might not be able to fully explore ZDR until you acquire the Screw Attack^*, and you'll also need the Power Bombs if you're aiming for 100% completion. In fact, the Power Bombs are acquired not long before you need to face the final boss. Therefore, you'll need to do some extensive backtracking if you're aiming for 100% completion.

^*: If you're sequence breaking, it's possible you haven't acquired the Space Jump yet. You'll need that as well, if you want to reach every nook and cranny of ZDR.

Solution 2:

Nothing in Dread is missable. The game likes to stop you from backtracking to help prevent you from getting too lost, but these blockades will all be circumventable as you get power-ups. You won't be able to get 100% until you're basically at the final boss's door anyway, so might as well wait until you get into the final area and reach the final elevator, since at that point all the Teleportals become interconnected and backtracking will be much easier.