I would say that if you are outside of the rating range of the tournament before it begins, you should probably withdraw to be fair to the other players who are looking for games with those in their own rating range.
a silly question about withdraw

no doubt that i will do it, i was just wandering if there is any rating related, downsides to it or does it merely cancel my entering the tournament?
I believe it automatically will move you to the correct tournament if it is an offical chess.com tournament, If thats the case don't worry about it.
i started to play online chess only recently, as my rating grew, i outgrew my second tournament for which i registered (i registered for 1200-1400 rating, while i'm now 1550+...
the tournament hasnt started yet. are there any downsides or negative side-effects if i withdraw from the 1200-1400 tournament before it starts. is it like a simple cancel, should i say?
sry if its a bit silly question...