Correct, scuffing helps to airiate the hull.

what about just sharpening the keel
any impact? worth it?

I have a notched transom, would you just sharpen the notched area, or anywhere in front of the (twin) drives.
I have some nicks to fill and a previous boat name to take off the transom, might have the glass guy quote sharpening the keel if it helps

speed is low/mid 70's right now on a 24 deg non step
( formula 336)

Ramb

oops, I meant, sharpening the Transom

Ramb

sharper the better will it increase speed? who knows.

The back edge of the hull at the transom if it has a radius it can suck the hull down into the water. A sharp edge there, should allow clean water to the prop(s). That is a good thing!
My buddy sharpened his on his 28' and saw a speed gain.. dont remember how much. So it is worth trying.. .02..