Replying to Advice on 60fps editing

#1 - So I shot a bunch of stuff (70%) in 60fps.  In Final Cut I was planning in editing in a 60fps timeline.  Now when I speed that to 50% in my timeline the slow mo looks good but is that the best quality it will be?  Should I convert outside of FCP and then import or is what I did in FCP adequate?

#2 - Now I also have 24fps footage.  Should I just drop this in the timeline and render it or should I convert outside of FCP and then import to the timeline?

I know this probably seems mundane to some of you but some quick advice would be helpful.  I wan't to get this edit started on the right foot.