Are the card rewards you get while playing in modern still soul bound, or can you now trade them for active rewards, also I want to ask, how much would you need to buy a deck to compete in modern, at the moment?
The rewards aren't worth that much. The cards from modern/glint shop are soulbound, but the Frontier cards aren't. There is also a chance to get a scroll that unlocks the cards from the advancement chests. At this point, I think it's better to play Frontier and get those cards, as you can use them in Modern. You won't be able to move up that far, though, unless you want to level up a decent amount.