You have quite a few options on how to set up your system. I’ll tell you how mine is, and maybe it will give you ideas on what you want to do.
I run an HDS7 at the console, and then have an HDS5 that I move between the bow and the transom.
Under my driver’s console, I have the LSS1 mounted along with the NMEA network backbone. I have ethernet connections off the LSS1 that go to the HDS7 at the console, one run to the bow, and one run to the transom location.
The transom location is just a power connection and the ethernet connection. When I have the HDS5 back there, I run the downscan off the LSS1 and have the side scan running on the console location.
At the bow, I have power, an ethernet connection, an NMEA connection, and a universal sonar connection off my trolling motor. I can either run side scan or the regular sonar off the bow mount.
I also have an NMEA connection to my e-tec so I can see engine stats on my console unit.
So, what I needed for parts to set mine up was the following. HDS7, HDS5, LSS1 (comes with one 15 foot ethernet cable), 6 foot ethernet cable, 25 foot ethernet cable, NMEA power cable, extra head unit power cable for transom location, evinrude interface cable, and a 15 foot NMEA cable (to bow).
I think that is everything.