Atari is a tough animal and we are nowhere near being complete on those categories. The amount of variations is insane and the other issue is that EU and NA are interchangable, and after all these years there still seems to be confusion as to what came out where. As a result, our VCS categories still have NA games in EU section and EU games in NA section. So be aware of that.
If you have a cart and cannot identify which release in the DB it goes to, it is best to ask in the forum for ID help for them.
Please be careful to not make dupes and to not try to convert existing entries to what you own.
As far as a resource goes, Atari Mania has the best resource regarding carts, variations, where they came out and what boxes they originally came in.