Some one must be PIC on the aircraft. And you must have some system that states who is the PIC. Tech log is the usual way when the PIC signs the aircraft out.
There is no problem logging hours on none EASA reg aircraft. They all count as long as you log them according to the EASA rules. So any hours in Cessna pippers or any common training aircraft do count. Its when you get into microlight type aircraft you may not be able to count them towards the pre course requirements for cpl.
If you had an instructor next to you then they are counted as duel unless they were nothing to do with the flight and you were transporting them somewhere but I suspect that the instructor will have booked them as PIC as well so you won't be able to use them.
If your solo or don't have an instructor next to you, they are PIC.
Forget anything to do with hours logged as safety pilot in the RHS they won't count.