I had a Motorguide Xi5 on my last boat, that worked with the Lowrance fish finder. I mostly used the remote to control the trolling motor. The spotlock for the motor worked well, the GPS was built into the head of the motor. I actually think the Motorguide kept me pretty close to where I set it. I seem to do more drifitng around with my Garmin force now.
To be able to control the Xi5 with the fishfinder I had to set up a NEMA 2000 network between the trolling motor and fishfinder. I don't know if that is still true with the newer graphs or not.
I have all Garmin on this boat. I assume I could control the Force trolling motor with the Garmin Fishfinder, I haven't tried I just use the remote. I keep the foot pedal in the boat in case I need it but I've never used it.