is it still useful to play SM64 on phone RetroArch using Mupen64 and an Xbox bluetooth controller to practice when my pc isnt available? because i have to go places often and dont always have my pc alongside me, (its a laptop but battery is ass) so i would like to know if it is still a viable improvement strategy.

I'd imagine that's entirely subjective, so give it a shot and see if you feel like it helps you. It doesn't really matter whether you are playing on an allowed emulator or not as long as you are not actually submitting runs from it.

If it’s only for practice then yes that’s fine, practice however you want

kk thats cool.