The wake from a boat with an outboard looks like the wake from most boats. They're all pretty similar really. Depends mainly on the hull whether the wake is wide or steep or whatever...
With no weight in the boat the wake will definitely get smaller going from 21 to 23 mph. It might also lengthen, meaning the spot on the wake where you get the best pop could shift.
Do you have any kind of extended tow point? I used to ride behind an outboard fishing boat with no tower or ballast and we had to tie off to the ski cleats on the transom. That would often cause me to break at the waist due to the low pull when I hit the wake. Also instead of pulling you up off the wake the rope tends to pull you down instead. Make sure you are standing tall, shoulders over your hips and hips over the board when you ride, that'll make sure most of the tension on the line is transferred through your body to make you pop off the wake.