I’m not a big PVP/PVE guy here in WoW so the only information you’ll get out of me is all about roleplay.
Horde RP is mostly guild based but the casual roleplay can be found at Orgrimmar (Valley of Honor) and Silvermoon City (stay on the east side of Silvermoon…). The average player usually logs in for roleplay at about 7:00pm - 8:00pm realm time so I’d start taking a look around then.
The thread that Jianyù referred to can take you to the thread for Terrace of Tribes, a big ol’ discord for troll roleplayers but make no mistake, there are plenty of RP discords out there based on the kind of roleplay you are looking for: faction, class, race etc.
I don’t have an encyclopedia of every active RP discord out there, but I’d make a start in your search by joining Argent Dawn Discord. There are PVE/PVP folk in this discord as well so you can also look for like-minded players who want to do whatever in this realm.