I'm not sure what the differences are over the elite as I've never used one.
If you have a modern engine you can hook it up to the hds via a nmea and engine interface cable and get real time information off your engine. Fuel flow tachometer engine temp trim etc.
Yes you need two transducers
The structure scan transducer is long and skinny. About 200mm long. This will give you down and side scan. Then you need a normal tranducer and depending on the type of fishing you do would depend on the size you get.
I've got the 50/200 but on a good day I can pick up browns. Id like to get the 1 kW tranny but they are about a $1000 so might put up with mine a bit longer.
It is pretty simple to use as well and when you troll all day like I do and your mates love playing with all the settings. It's pretty easy to return it back to normal.