Welcome to Moon Guard - we recently transferred here as well (from Emerald Dream) and have had a great experience with the community so far.
What kind of RP do you think you might be interested in? There’s a huge variety of guilds from scholarly, military, mercenary, public service, etc. The suggestion of the Stormwind Fair is a great start - you’ll get to interact with members of the various guilds while there.
The other question you might want to ask yourself is if you’re also interested in other forms of content such as PvE and PvP. Some almost exclusively RP, while others do a combination of activities.
As for us, we do a mix of all three - we are primarily a Military RP guild but we do quite a bit of both PvP and PvE content. We run battlegrounds and/or arenas almost every day, Torghast almost every day, do patrols in War Mode. We’re also going to start doing Castle Nathria with some friends/allies soon.
https://us.forums.blizzard.com/en/wow/t/a-rp-pvp-kul-tiras-marines/785778