This is as I understand it:
1. WOT is a range that the manufacturer sugests that you maintain for best performance and econimy, which is governed by prop size.
2. Maximum revs is usually the upper WOT figure. ie: if your manufacturer suggests that the WOT range is 5000 - 6000rpm them maximum is 6000rpm. Most outboards have some kind of rev limiter to stop over revving if the boat comes out the water anyway.
3. If you under prop, your revs will exceed the WOT and could damage the outboard, but initial acceleration will be very quick.
4. If you over prop, your revs will be under WOT. You'll have low acceleration and be labouring the outboard and potentially will cause more damage than under propping ie: holeing pistons and wrecking piston rods and bearings.
So match the prop to the recommened WOT for your outboard/boat combination and be mindful to the fact that as you load the boat more heavily the maximum revs will drop.
I'm sure that someone will say I'm wrong
Borrow a load of props of different sizes and go do some RIB testing.