I just made a couple of tests:
Launchbox 13.16
Nointro set based on the current datomatic dat
Region priorities: USA, Japan, Europe
Sega Genesis:
Micro Machines - Turbo Tournament 96 (Europe) (J-Cart) is taken as main rom, where it should be Micro Machines - Turbo Tournament 96 (Europe) (Rev 1) (J-Cart).
Super Nintendo:
Donkey Kong Country (Europe) (En,Fr,De). main rom, where it should be Donkey Kong Country (USA) (Rev 2)
In general, it often ignores region priority, and latest version.
There is no way to manage custom priorities (for example, for older consoles the best version is usually the japanese one with english language/translation)
I really love launchbox, and it works really well with 1g1r collections, but i'd like to see a better rom import implemented for full sets, maybe a no version of the "import mame full set" function.