It’s smaller than Horde and walk-up can be found in the evenings in Duskwood. For Stormwind, walk-up can be found if you put out the LFRP call and folks will come out of the woodwork.
As for RP itself, it’s vibrant within guilds and pockets of the world where folks gather, we just don’t have the Valley of Orgrimmar equivalent. Joining the Wyrmrest Community Project is a great way to network and enjoy the small neighborhood feel that is WrA Allianceside as well as connect to the Horde and Neutral side of things.