is the season pass worth buying at start of season (is it only maps that contribute?)

Hello again, Guys... Been away for a few years, this time.

The season pass mechanic looks good. I like the armour set, etc. We can't even progress with it till maps though, right? So should I just wait to buy it?

Would be awesome if someone could explain how it works properly, as really not sure if I need to start completing it now, or if it is just based on maps?

Thanks.

PS: do the chests have dupe protection on them? I think I only need the gloves for the owl set, from the first one (from back before dupe protection on chests) if that is indeed the set I think it is.

If they have dupe protection, then likely is very worth it for me.