Stripe for membership plugin and trouble setting up for individual sites

Two things:

1) Wondering why the membership plugin doesn't offer the payment gateway stripe...?

2) I have a pro-sites set up, and I wanted to install the membership plugin into one of the subsites. So i installed the plugin, DIDN'T activate it, and then as the admin, manually activated the membership plugin for the specific subsite. However when loging in to the subsite as the subsite user, the membership plugin doesn't show up...do i have the wrong idea about the plugin? Please advise, thanks!