Roleplay is just another means of spending time in game. Roleplayers do use every content available to them, but when they don’t do content then it’s roleplay. People stay in character and follow the general rules of roleplay.
You don’t have to dedicate yourself to roleplay in a specific time window. You can roleplay every single day or once a month, doesn’t matter really. The point is you are interested in roleplay.
Your player character is not the character you make up. Your player character might have defeated Sargeras and stuff, but your character that you portray in roleplay didn’t. Create a level 1 character for Horde or Alliance, have a look around at the various hubs (the TRP3 addon has a neat map scan addon to find roleplayers) and see if you do like it.
Nah, that’s OOC (out of character) content. TRP3 has a neat little button where you can switch from In character to out of character. You don’t have to be in character 24 hours a day.
In short: roleplay realms are just the regular game with all its features, but people come together to roleplay as an additional activity.