Hi mods! I did my best to not TL;DR but let me know if anything is unclear.
How he uses powers: As a general rule, Quentin uses his powers first and foremost to show off and to spite people who hefeels have wronged him (ie basically any authority figure). These days he is particularly fond of psychic guns and flying. He also consistently refuses to do things the way the older generation of telepaths does them: tweaking memories and implanting suggestions and reading minds to fix all their problems. Quentin plays mind games just to have a "gotcha!" later, reads minds so he can gloat about knowing more than you, and he very much enjoys finding unconventionalways to use his powers to really stick it to older mutants. At his most malicious, Quentin is a troll, but he also does nothing to avoid the consequences of his actions other than storm off to go sulk somewhere. He wants a reaction, and he wants that reaction to be genuine. Worth noting also is that he appears to be generally less gung-ho about using the more privacy-breaching/agency-removing of his powers on non-mutants (when he's older and less let's-genocide-the-humans-y) or just people he doesn't have beef with. The implication is that a) he's to at least some degree mindful/respectful of the power imbalance between himself and people with weaker or no powers and doesn't feel inclined to punch down and b) he feels the need to be more hostile/defensive around many of his fellow mutants. (Or it's just inconsistent writing but I'll take what I can get.)
Limitations:
Boy done got nerfed. At his current canon point, Quentin has been nerfed by story events. As far as how I've interpreted the power nerfing, it appears that he can pretty much do everything he could before, but it takes more effort, he can't maintain constant use of his powers for as long, and anything blocking him will be much more difficult if not impossible to break through.
He's the dumbest smart kid ever. Due to spending his adolescence rebelling against The Establishment, Quentin has little to no training from more experienced psychics and pretty much makes it up as he goes. He has a lot of power but very little understanding of how to use it.
Look at him, he's scrawny. This isn't necessarily a limitation necessarily, but it is a balancing thing. Quentin is a squishy mage. And when you take into account that he values being flashy over being smart, what you get is a really squishy mage who getssquisheda whole lot.
The Plot. The biggest limitation on Quentin's powers is that sometimes the plot needs them to not be as powerful. Writers will just slap a vague “psychic block” into stories and not even bother trying to explain it any further.
In Game: Honestly, I was planning on leaning super hard on limiting him via vague plot BS. A universe where random people from other realities get pulled in for some kind of penance self-reflection stuff? Wow that sure sounds like a place where answers wouldn’t be easy to get via telepathic powers. Mumble mumble psychic blocks mumble mumble a wizard did it. It ain’t that deep. I also picked a canon point where he's already nerfed and is relatively not an asshole.
Re: REVISIONS REQUESTED
How he uses powers: As a general rule, Quentin uses his powers first and foremost to show off and to spite people who he feels have wronged him (ie basically any authority figure). These days he is particularly fond of psychic guns and flying. He also consistently refuses to do things the way the older generation of telepaths does them: tweaking memories and implanting suggestions and reading minds to fix all their problems. Quentin plays mind games just to have a "gotcha!" later, reads minds so he can gloat about knowing more than you, and he very much enjoys finding unconventional ways to use his powers to really stick it to older mutants. At his most malicious, Quentin is a troll, but he also does nothing to avoid the consequences of his actions other than storm off to go sulk somewhere. He wants a reaction, and he wants that reaction to be genuine. Worth noting also is that he appears to be generally less gung-ho about using the more privacy-breaching/agency-removing of his powers on non-mutants (when he's older and less let's-genocide-the-humans-y) or just people he doesn't have beef with. The implication is that a) he's to at least some degree mindful/respectful of the power imbalance between himself and people with weaker or no powers and doesn't feel inclined to punch down and b) he feels the need to be more hostile/defensive around many of his fellow mutants. (Or it's just inconsistent writing but I'll take what I can get.)
Limitations:
In Game: Honestly, I was planning on leaning super hard on limiting him via vague plot BS. A universe where random people from other realities get pulled in for some kind of penance self-reflection stuff? Wow that sure sounds like a place where answers wouldn’t be easy to get via telepathic powers. Mumble mumble psychic blocks mumble mumble a wizard did it. It ain’t that deep. I also picked a canon point where he's already nerfed and is relatively not an asshole.