Here is a good place to start, the Alliance RP Discord. The various RP guilds have channels in there where they can pin information and be messaged for more information.
https://discord.gg/VUY4Fpd
A lot of good RP guilds out on alliance side with a mix of PVP and PVE to varying degrees.
This forum post leads to a great spreadsheet for both Horde and Alliance guilds:
‘2019 Emerald Dream Guilds At a Glance - Updated!’
I hope you find what you are looking for 