You aren't gaining any more cards than you had
Because the deck doors and tray cover flaps are fully magnetic, you can swap them out for different colours if you have multiple Strongholds, though that shouldnt be a primary reason for picking the Stronghold
Then you can run stuff like proliferate, the +1/+1 countered stuff getting deathtouch with Mer-Ek Nightblade, and loads more
Theme decks and booster packs will also have in-pack codes that will unlock virtual cards for use in the online game.
Expect Kithkin, boggarts, merrow, Elves, creature synergies, new and returning mechanics, and art that leans into the whimsical side of classic MTG
Hypno Splash is also quite an effective move, as it not only deals a decent 160 damage but also puts the opponent's active Pokmon to sleep