In EVE, you'll be able to fly up to cruisers for a single faction and have a limited set of skills come November's release. This is certainly not going to impact your ability to make an impact in PvP if you want to. (Most PvP is done in cruisers with more or less basic gear.) If you want a larger corporation or an alliance, at least the CEO is going to need to be subscribed. I'm not sure if there's going to be any other restrictions other than skills available as nearly everything is skill or standings related.
Not to hard to play off PLEX if you can find a way to get the in-game cash every month, though last I was playing the prices were up so high you had to run scams or get into some pretty limited sections of the game you're not going to be able to be a part of strictly as a free player. (And I see they've nearly doubled since then.)