GTAV is a totally different game and I have confidence that R* realizes that what may have worked there, won't necessarily work in an RDR environment. We've already been told that certain elements will be different like the radar system. ......which will only show other players in the immediate vicinity.
Personally, I'd save any feelings of angst until the next teaser trailer releases which I believe will cover multiplayer.
In either case, I don;t think R* is stupid enough to attempt to create a GTAV:O experience in RDR2:O. In either case, I am sure there will be different online features for those who prefer a more coop playstyle over PvP.
You say this will be your first R* online experience? If so, I have to ask..... What are you basing your judgement of GTAV online on? Yes, there is a lot of griefing/silliness but in that game, it is actually encouraged and (like it or not) it fit. However, RDR2 isn't the same and I don't see R* treating it as such.