It's not that simple as that in Germany. Under 7.5t combined weight you don't need to use the trip recorder. Hook an empty trailer to most any C1 truck and you have to put in the card or start the computer.
You do have to pay tolls if you are transporting something, regardless if it's private. There are only two relevant (to us) toll exceptions, the vehicle can't be used by construction to transport cargo or it is registered as a historic vehicle. That means a truck modified into an RV (you have to have the change documented in the registration papers) doesn't pay tolls, regardless of tonnage, as long as it doesn't pull a trailer (even empty) or has a internal space dedicated to carry cargo. Driving your snowmobile in your RV garage represents carrying cargo, there's a EU lawsuit about that.
The is a separate exception for combined horse and living trailers that have a living space that's greater then 50%.
For boat transports the historic vehicle is the only way to not pay tolls.
But, and here's the catch, this is national interpretation of EU law and it doesn't work in another country. Cross the border and the new country can request you to use a trip recorder or pay tolls or not drive on sundays, etc. This applies both ways, come into Germany with a polish truck converted to an RV or sporting yellow plates and you are equally exempt.
