If I was you, I'd install the 1198 on the console with the transom
SI transducer first, and get those dialed in.
That will take you some time. You may have to move the transducer around
a bit to get the very best performance out of it.
Some people worry about high speed depth readings. You may or may not be
one of those, but if you are, you may have to get a thru-hull transducer for that.
You can't just bolt this stuff up quickly and expect to get the very best from it.
With this initial set-up you can check for any interference with
other electrical devices on your boat.
After you get some experience on the water with that set-up,
then start thinking about the trolling motor transducer and switch.
Then, you can start to deal with interference issues (if any), caused by the
trolling motor.