I'm on my first playthrough of Pool of Radiance with GBC. Without GBC, I don't think I'd be able to play the game without the automapping, encamp - fix, auto ID.

But I wonder if GBC is cheating, particularly with the level drain fix. I feel a little less bad when there is seemingly no way, from my research, to get Restoration until late in the game? Isn't this a bit useless/encourages grinding? It seems like maybe that's why level drain is so common, like the designers wanted to extend the game. I know no temple does Restoration, and I have several scrolls with Restoration (7th level) but my party keeps getting level drained and it doesn't seem like I'll ever get to the level where I could cast Restoration.

Any seasoned players that can shed light on this? Should I also see encamp-fix as kind of a cheat since you can rest anywhere without negative consequences?

You should get enough scrolls to cover your needs.
Also, make sure your front guys have decent AC. Don't be afraid of using the Hero hireling.

And make sure you cast Restoration before you are level drained again. IIRC it only cures one level drain at a time, and things can get buggy if you need to cure several levels.

The classic way to handle level drain is save/reload, just save the game before a dangerous encounter and reload until you don't suffer from effects which aren't easily curable.

Level drain fixing with GBC can be disabled from the SETTINGS -> FIX DRAIN ON/OFF.

At what level can I use them?

Any level. They are not level restricted. Level restrictions applies to memorizing and casting spells, not reading them from scrolls.

I did not know that. Thanks.