Just picked up the RC setup in the past week so can answer your questions.
The RC box has only the RC screen, nothing else except a quick start card. So yes, you definitely need the install kit. Mine is a 2019 so there in no moving of pins from the connectors, it is plug and play. The install kit contains the mount and dash covers, Ft + Rr cameras, an air temp sensor, radio adapter harnesses, radio antenna, GPS antenna, and a lot of other misc needed screws, wires, and zip ties. There are a lot of parts and wires but it is plug and play. I also bought the new V2V antenna and a SSV 3 speaker system to go with it. Now the fun begins.
It looks intimidating but if you take the instructions and lay your parts out, it really isn't that bad if you have some mechanical aptitude. The pic below is of the RC, install kit, and V2V kit. The SSV kit has it's own set of wires that go with the amps and speakers.
If you buy, be sure to use the $150 Polaris Accessory coupon.