Hello and welcome to the server! We get new people all the time, and new threads always pop up to replace the old ones. Not that I’m complaining! It’s always good to see fresh blood coming into the community!
Moonguard is indeed a large and active server, but it’s Horde population is decidedly smaller compared to Wyrmrest Accord’s. Alliance side, it’s the opposite. There’s plenty of RP on both sides on both servers, but many people prefer Moonguard for Alliance and Wyrmrest Accord for Horde. That doesn’t exactly tell you who you’re going to get along and enjoy RP’ing with, though, so the best method is generally to roll up alts on various servers and try them out until you find what you like.
Voice RP is rare in either case, but it does happen- usually via Discord.
The following link has a handful of the many Horde guilds actively looking for new members, and you’ll inevitably bump into even more as you get to know people in game.
There’s also Friendship Fundays, a community event aimed at new/returning RP’ers.
I hope your search goes well, and once again: welcome to the weird and wonderful world of RP.