WrA-Horde does indeed have an active RP scene with a diverse array of RP guilds, and several guilds that raid and/or do Mythic+. There are many more guilds on the server than are represented in this thread, but WrA Information & Directories (Guilds | Communities | Events) is a good place to start looking.
If you’re looking for walk-up as well as guild RP, it’s also a good idea to roll a level one alt over here and visit the main walk-up RP hubs (the Wyvern’s Tail in Orgrimmar, and most districts of Silvermoon City) to guage the atmosphere for yourself; peak activity tends to fall between 6pmish and 8pmish server time.