Hoarder's Cave

I've also toyed with the idea of collecting the manga, but as you've stated the cost...
Also what do you mean by arc headers? I know there have been misspellings here and there but I can't think of anything major.

 

look here
At some point they started printing the volumes with the names of the arcs at the top but they half-assed it. When New World started they just called everything New World, instead of breaking it up into Fishman Island and Punk Hazard and stuff. This really bugs me, though it probably won't most people.
I haven't looked at every volume to see just how bad it is, though I've seen some and it's apparent that they're not putting enough care into it to be accurate so whatever.
I know the ones that I had said "East Blue" at the top so perhaps they're doing it by overarching arc, but that doesn't quite work either.

I also noticed that in early volumes the grunt pirates used really generic, typical pirate vernacular which bugs me as well since that's not how they actually talk in One Piece. I don't know if they kept doing this in later volumes.