These units are drop in replacements for any current product. The exterior dimensions and connector types and pin-outs are identical. They are marked clearly as V3 units. They do require a new antenna for Multi GNSS capabilities, but can use pre-existing RaceGrade GPS antennas if they are not subscribed to Multi GNSS.
The basics are that the performance without the paid-for Multi-GNSS option will nearly identical to the V2.1 device with a few software perks.
With Multi-GNSS enabled the unit uses GPS, GLONASS and BeiDou;