Card games are generally played with 10-20 cards once you hit your mid/endgames. I can't think of a system where you'd have mechanical benefit of all those being epaper before you should go full digital. Having a few choice mechanics tied to them is the way to go.
What does epaper get you that paper doesn't? A microprocessor and persistent state. RFID cards on a board game might be a good middle state for most cards. Scan them as played. Build gamestate or dynamics to be populated to epaper.
Epaper would be good for storyline branches, timeline progressions, evolving characters. Make them traveling characters being owned by different players. Differentiate them from becoming a static scoreboard that could be represented on a single tablet.
What does epaper get you that paper doesn't? A microprocessor and persistent state. RFID cards on a board game might be a good middle state for most cards. Scan them as played. Build gamestate or dynamics to be populated to epaper.
Epaper would be good for storyline branches, timeline progressions, evolving characters. Make them traveling characters being owned by different players. Differentiate them from becoming a static scoreboard that could be represented on a single tablet.