Are items in question blocks in Mario Maker 2 globally loaded?

Items do not count towards the active Item Limit while inside blocks, regardless of if they're in the loading zone or not

Powerups have a 100 item limit (per area, so 200 per level). Once you hit that limit, you're prevented from placing any more, but by placing the powerups into item blocks (or Bullet Bill launchers), you're potentially able to place up to another 2000 powerups. If there are 100 active items in the loading zone though, hitting the item block will just show a 'poof' effect as nothing comes out. Comsuming powerups within the loading zone when the limit has been reached will allow you to once again obtain items from blocks.

Gif demonstration below:

Here you can see that there are 100 stars placed in the area to the right, and I'm unable to place any more powerups. By adding the stars to the question block, the stars no longer count towards the entity limit, and I'm able to add powerups till I hit the entity limit again.

Trying to get the items from the question block while the 100 powerups are in the loading screen causes the new powerups to 'poof' and not appear when the question block is hit.

If the powerup limit has not been reached within the loading zone while it has been reached for the level, hitting a block will give the item inside. Additionally, if the item entity limit has been reached outside the loading zone, you are still able to get items from blocks, and in the case of moving items (such as stars and mushrooms), if they move into an area where items have been placed to reach the entity limit all within the loading zone, you'll actually be able to exceed the entity limit (I was able to get 103 stars in the loading zone with that trick).

Source Youtube Video for entity information

Edit 2: Turns out I was a little bit wrong with my knowledge, but also right with my answer; it depends on the item you're looking for. I tested it in SMB1 and mushrooms will stay loaded in but a POW block will disappear. Fire Flower and the Star stays, whereas a Goomba will despawn. So for whatever you're trying to spawn from the ? block, you'll have to test it out in a world and see.

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If your question is: Does an item that comes out of a ? Block stay globally loaded after popping out, then I am pretty sure the answer is no, unless it ends up on something that forces it to stay globally loaded like an icicle. Using icicles will force whatever is on it to be globally loaded so it would give a false positive.

You can try testing it real quick, honestly. It's super easy. Create a blank slate level and have the ? block spit out a mushroom or something, and have the mushroom get stuck in like a 1 block gap right next to the ? block somehow. Run like a mile away, come back and check. If it's there, it's globally loaded. If not, then it's not. Just make sure you trap it using like.. Normal ground or something (see above about icicles).

As a side note, you can also try having the item stay stuck on the ? block it came from as well to test and see if THAT makes it globally loaded as well. Still, I'm pretty sure that's not the case, but I don't know as I've never tried.

Edit: Just in case I missed the question.. If you are at the sprite limit and you are remote activating a ? block to spawn an item, it does count towards the sprite limit. Your item will not spawn and will poof like the items do in the gif posted. If the sprite limit is not reached yet, then check the results of the test above I gave you and see how that goes. I'd test it myself but I gotta get my Switch handy.