@P.Fonseca Thanks, forgot about that topic. So do you agree with my statement:
"So it means the safe way to go is just to assume that the base unit in FrontEnd is pixel. But when printed it will behave as defined with correct printer points."
The first part seems to be proven but about the second, I don't know if MMA respects printers dpi (maybe it doesn't matter, I don't know I don't print so much :P)