The fact that communication is "live" than posting here lets you plan or communicate things quickly is probably the most convenient thing along with being able to ping people and whatnot. Other than that I'm pretty agnostic on a discord. Like people like it and it has its uses but I don't find it nigh-essential to have. As for a generic structure for a server, an on-topic and off-topic server are pretty all you need. I don't see the RP as being that big and complex that you'd need multiple sections dedicated to the rp. But, if you wanted to get fancier, you could do on-topic and a channel dedicated to planning in case you don't want stuff to get lost in chatter.