Way to much stuff to do

If you grind it the comp pass gives the best rewards of all the options in my opinion. You can get a good mix of coins, packs and season xp from the comp pass.

Legends and AKA solos will eventually have a pretty good reward of a presumably high ovr player. But there currently aren't enough challenges to get tokens for high ovr players. While you don't necessarily want to be behind on these, they currently aren't very rewarding if you don't have much time to play. They're probably the least rewarding of all the options you listed.

Treats can get you some good rewards. But unless you're winning super bowls in the h2h event, the grind for them is pretty slow and tedious.

At the end of the day do the whichever one you would enjoy most.