I think it is advised to join OOC hub guilds. Otherwise it can prove to be difficult to make new contacts and stumble upon RP. Plus as a guild member you get to be informed of RPs underway and upcoming events first hand. Here is a link to the active EU-PC hub guilds, marked with green next to their names:
PC-EU OOC Hub Guilds
Clans of Skyrim
As to RP spots, there is Wayrest, but most of the time people communicate OOC and meet up at an agreed location. About to IC guilds you better ask in the hub guilds OOC channels or in-game.