You can freely mix cards from different regions without any storage or gameplay issues
You inspect corners, edges, surface, and whitening under good light, and when you are torn between two grades, you pick the lower one
YES 025 Dvoreur de vitalit Vitality Eater Parkinson, VDB Privately produced card 2000-
Also, barring special sets where you cant get loose packs or booster boxes (Crown Zenith, GO, Celebrations, etc.), you usually dont need more than 1 Elite Trainer Box
(Put it onto the battlefield face down as a 2/2 creature
Revealing the Pack arts, Shining Fates Elite Trainer Box, Shining Fates Tin, Shining Fates Premium Collections, Shining Fates Mini Tins, Shining Fates Pikachu V Box and the Shining Fates Mad Party Pin Collection