We use both methods. For really short trips (under 50 miles) we have left the RIB dinghy on the swim platform, removed the standoffs and lashed the dinghy to the transom. I really do not like doing this as it negatively impacts the handling of the boat on trailer, impart due to a lighter tongue weight.
On anything more than 50 miles, we remove the dinghy and put it in the 6’6” truck bed. Dinghy bottom up and transom to the cab with nose of the dinghy pointing aft. The dinghy fits snugly on the truck bed sides and you can store a lot of things underneath it. Properly tied down the dinghy sits rock solid in the truck bed at all speeds.
I can get the dinghy off the davits and into the truck bed by myself. But getting it back on the swim platform at the end of the trip definitely takes two people and some patience and some muscle.