Has anyone experienced any issues having oAuth 2.0 active regarding other non-oAuth 2.0 connections? I'm pretty sure the protocol should be fine to activate, but my boss is concerned that there may be an impact on existing web services (SOAP, and oAuth1.0 with TBA, etc.)

I haven't done 2.0 as of yet but the type of Oauth is controlled on the integration record. The implication to me is you can have one integration using oauth 2.0 and another using oAuth 1.0