I've been in a relationship with a women and if I don't want to be penetrated (which I don't) then that's completely fine and doesn't affected anything too much.
sex with every woman is not the same
just as sex with every man is not the same
make sure you are very clear with any woman you consider sex with that this is an issue for you. enough women in same-sex relationships consider penetration to be part of their sexual relationships that you need to be upfront about this