Thanks a lot for the feedback.
For the card limit, it should be the "Board Cap" upgrade that defines how many card can be on the board at once. Are you referring to this?
Regarding the deckbuilding, yes this is what I'm currently working on, it will be added soon. You will be able to obtain:
Jokers: can be manually added to the board to affect nearby cards
Card Modifiers: modify each card to change how it behaves when flipped