When you are BLDing you can't see the cube. When eyes open then you see that it's solved. You can use cancellation though. Actually in the end of R perm there is a U turn. And on BLD I never even tried to memorize that IO don't have to do it. I'd rather do the FULL R perm and then U'
2 corners swapped, 2 edges swapped, and whatever third one you're thinking of, can be solved by just switching two edges and then doing PLL (2 opp corners swapped with 2 edges swapped is an N perm)