I have a 16' mr pike with a terrova 12v 60" us2 I pilot and an 18' Lund fisherman with a terrova 24v 60" us2 I pilot.

1st for I pilot- you need this for walleye fishing. I have foot pedals for mine and have used them 2x in 5 years, I only use the remote and I carry a spare remote battery on board. Going slow <1.5 only electric unless fighting wind/current. Remote has heading lock and cruise control, that's what I use. If going faster or for a longer time >5hrs then I use the kicker for extra power and let the heading lock steer, set the cruise for 0.1 mph faster than the kicker.

Us2 (built in sonar)- you dont need this for open water trolling, it's nice for jigging structures. I use mine in canada when jig and minnow fishing.

Shaft length- this is also important. Get the longest shaft you can. My 18' lund has the 60" shaft and its honestly too short for anything remotely rough, it pops out of the water. Might be only able to get the longest shaft with the highest power motor.

Power- again bigger is better IF you have room for all the batteries and get the biggest batteries you can. Hard to find group 31 but 27 are all over.

Ulterra vs terrova- meh. I have read reviews of some ulterra stow/deploy motor bracket issues leaving the motor unable to stow. If the lake kicks up I wouldn't want to be dealing with that. If all I did was troll erie then I would honestly look into an Auto Pilot with speed control for my kicker.