We don't want to implement epi Commerce. Can we still install the epi PayPal provider and use it?
I don't think that is possible. The classes in the Episerver PayPal provider reference a ton of Mediachase.Commerce namespaces & Commerce Workflows and you also have to wire up the provider inside of Commerce Manager to get it to work. If you are simply looking to accept payments via PayPal Express on an Episerver CMS (or any site really), it's not terribly difficult to implement. PayPal has some decent examples on how to do it on their website.
Hope this helps!