Does GBC have any better clockspeeds or changes the gameplay in any way other than adding colours? If not then I am guessing it should be viable for runs, right?

All Gameboy consoles (except GB micro) are perfectly fine for running the game. The main consideration is how easy it is to record, assuming you want video proof

Edit: thought this was a different leaderboard lol, video proof is required for this game so you'll definitely need to be able to record your runs

Well then, that's easy. Time to do runs on an unmodded GBC :)