Card size, which would be playable

Hi there

I'm running through a game design where players would build the map from cards. Each 'land' can be modified by laying other cards underneath so an edge of the card would be seen. Any land cards not used to create the world would be used to make up an action deck.

so cards need to game board, board modifier, and action deck

I would like the players to be able to sleeve the cards if they so wish.

Would
square cards (80x80 or 70x70mm sleeves)
'postcard' (80x120mm sleeves)
CCG sized (66x91mm sleeves)

Many thanks

Chris