Welcome to the Side Imaging Forums ezfishn.
1) There may be. The 2D sonar may interfere and so could the Si/Di sonar (this would more dependent on the direction that the trolling motor is turned). If you see interference on the 2D sonar you can try turning on and up the Noise Filter menu on the unit showing the interference.
2) Yes. It will allow for high-speed communication between these two units. You could have them share waypoints, GPS Receivers, temperature sensors and even some of the sonar between them.