The Silver Tarot Cards did one of 9 or 10 different things in battle, some good (double XP and gold, everyone does criticals), some bad (casts Defeat on the party), but after you went through all of the possibilities, you'd always draw the Terminator Card, which would summon a Necrodain. If things worked out, you could level up fighting them.
In the remake, they made it just randomly do crap over and over, usually the 'casts Defeat on Party' one, and the Terminator Card never showed up.
Party members in the wagon get experience yeah, but you don't always have the wagon with you in every dungeon.
IIRC, the medal on Taloon's ship is the only missable one. Medals work differently in the original 4 and in 5 than in the other games though, so each one is important to get in the NES 4. You cash them at the Medal King's Castle, not in a random well like in 3.
If you want to know how they work differently in this than in 3, just gimmie a hollar (or whoever else knows the game..haha I never get to talk about these games to people).