Yeah, the dub would kinda give that impression (despite how often they got the cards wrong pre-ARC-V [don’t quote me on ZeXal]), but 8/10 times, the animators get lazy and just either use a blank card-type-colored card or just literally put a card-sized block there. It’s an adventure. XD
Pfft, I honestly know just as much as you do. XD
AFAIK, Academia and the City in the Fusion and Synchro dimensions are essentially AUs of GX and 5D’s, respectively, and so Asuka, Ed, JACK, and Crow are AUs of their original series’ selves. There was some theory floating a while back about how Heartland/ZeXal is post-5D’s if Ark Cradle hit, while ARC-V is post-5D’s if something something Synchro and Xyz coexist. Hopefully we got some idea of this before the series ends!