I noticed the keel on my 86 Formula 242 is rounded by the transom vs the keel on my 377 Scarab is pointed. Why is this?

Ride vs speed. A pad bottom will be even faster. A sharp v cuts the waves the best. Pad is for speed. A round is in between.

Does that mean a pad bottom boat will ride rougher than a round keel boat? What is considered a small pad and what
would be considered a large pad? Approximate size please. Does the pad's width affect stability as well as speed?
So the small pad bottom would be fastest but inherently more unstable than the large pad bottom?

pads similar to what you see on Velocity and other boats aid getting on plane faster, adds more speed on top with the stern riding higher, less vetted surface overall . It's obvious that a V bottom like the scarab's in the picture above will give best ride in rough water. Another configuration like on my boat here with a V shape pad helps the boat going faster on top yet maintaining its rough water capability. The boat has 24* deadrise with less on the pad.

And what about pad keel with notched transom vs classic transom?

The pad, of course, increases top speed; But how much harsher is the ride when crushing waves? Isn't the notch to feed cleaner water to the prop and maybe allow higher X? It's downfall would be that it shortens the hulls running surface.

Is not pad keel there for bow leverage?

notched transom is for bow lift. And cleaner water to the prop.

Nice vintage thread!
What about average pad keel boat speed diference with or with out of good notch?
Pad keel help only at top speed when boat ride on or all around?