If i finish the game with a Renegade playthrough and then start a new game plus, am I able to change my class and if I play paragon on playthrough 2 will I be able ot have 2 clear saves.

You can't change your class, but your Renegade and Paragon points are reset when you import, I believe. Can't remember atm. You will have a seperate save folder for your second playthrough, if thats what you're asking