There is a fundamental dilemma about an E-wakeboard: the initial maneuver of getting on the board for startup using no assistance (tow rope & vehicle). I guess you could jump off a pier to the water below. That would consume a lot of power until you reach enough speed. Harder still, would be a wet start with board fully submerged and you in some kind of flotation vest. That would require the most initial power. I'd imagine the easiest power draw would be an initial vehicle tow to speed, then let let go of the tow rope under E-motor power.
You'd still need to account for a fall back into the water in every case. Either have the power to pick yourself up over the water, or wait for the tow vehicle to assist.
Wakeboard vs. Surfboard. The prior is more maneuverable. The latter would give you flotation. Fun factor? I think both would be equally fun.
At first, I thought you couldn't possibly do flip type tricks on an E-wakeboard, but if you were given perfect wave conditions you could power over the wave crest to perform it. Maybe. You'd have to account for the weight of the board for it to work.
On the otherhand, an E-surfboard (longboard vs. windsurf board?) would work in more varied conditions. You'd probably be relegated to carving type maneuvers, or if your crazy enough you could pull off a headstand with your pooch on the front :lol: .
Kayak? Jeez, you'd probably need perfect smooth water to even attempt a high speed turn. Unless, you use a "sit-on" surf kayak. They are designed For maneuverability.
Ok, after my rant, my gut tells me that a "sit-on" surf kayak aka "wave skis" would be the goto build.