Sounds like you're playing on native resolution or something. Go to Graphics/Enhancements/Internal Resolution: if you're on a new(er) build, you should be able to change it there. Games look roughly
like this on my end, the edges look fine to me. And I don't even use anti-aliasing.
As for performance, it depends on many things. The game itself, the build I'm using or even the settings. Games like REmake run full speed for me, while I sometimes get slowdowns with some of the more demanding Wii titles.