If i wear a 7 in reg. puma shoes would an 8 in hi tops be to big?

Depends on the shoe and your foot. But no, you shouldn't have to go up in size just because it a hightop, all things being equal. You should be able to try on your shoes before you buy them. If you are going to buy them online try them on at a store first. You don't have to buy them there.