If you don't already have a towbar (or more correctly the trailer socket) you are unlikely to already have the trailer module, although the wiring connections for it are already built into the car.
Fitting instructions from Volvo so you can look to see if it is installed:
https://accessories.volvocars.com/In...XC60(-17)/2014
The wiring you need is basically the loom from the trailer module to (and includes) the 13-pin socket.
https://www.volvopartshop.com/13-pin...17-16510-p.asp Is what you need ( best to check with VIN numbers, though.
Even if you have VIDA you will need to get the software via a dealer or independent specialist that has the 'online' VIDA system. You must have this if you are using the genuine system, which, as you say, is highly recommended, because nothing, not even sidelights, will work without the software addition.
Best to shop around for the software install- prices seen on here and the xc70 sections are ranging between £30 to £100+ for exactly the same service.
I don't think it is the fact that it isn't a V70, it is probably how all later cars are. Mine is an xc70 MY16 and had to go through all this hassle as well.