I'd have to go with Manny.
Floyd, however, is probably the most technically sound fighter of all-time, atleast IMO, so a fight between the two would be very interesting (although I'm 100% sure it will never happen).
That's a tough one honestly. If I had to pick one I probably would give Manny the slight edge only because his work rate is crazy and he keeps it up throughout the fight.
Mayweather is an extremely efficient fighter so he doesn't need to throw as many shots as Manny. I'm not to sure if he would be able to throw as much as Manny does for 12 rounds simply because I've never seen him do it.