Hey, on the left side are the cards I received from Japan. The right side are the English print counterparts from my childhood collection.
Mewtwo Promo 12 - this was the silver prize for the JR stamp rally in Japan. Gold prize was non holo black star eevee and there was also the non holo black star GB meowth. Because the English versions are holo and the Japanese English prints are non holo people tend to collect both versions as they are clearly distinguishable. But, people often overlook the mewtwo 12 because both versions are non holo. I’d be interested to know why they chose to change the other two but not this one. Anyway the difference is very minor. Japanese card stock and a slightly lighter colour purple, came in this booklet after completing the requirements for the silver stamp rally.
Mew 8 is the GOTTA! Magazine glossy mew. Was attached to a peel off in the magazine from Japan. Card stock and glossy surface are the key differences.
Mewtwo promo 3 is from the “Kanzenban” VHS release of the Japanese release of Pokémon mewtwo strikes back. Came in the VHS along with a poster. The card is different stock, but also a much lighter colour, which surprised me how different it actually was.
There are people here that know a LOT more than me about these cards (I literally only knew of their existence in the last month). But I’ll try post some links that were shared with me that help give more info.