My main Tumblr presence of late is in the roleplay community. No, not sexy roleplay (at least not for me); the best way I can say it is freeform collaborative storytelling. Each person picks a character and by putting your character with someone else's, you create all kinds of interesting things. I used to do this on LiveJournal and Dreamwidth, but Tumblr has an odd strength in that it's very difficult to change muses.
Tumblr, for those who don't know, is a blogging site sort of like if Twitter took away all its restrictions on character limit and post type. You follow people; you have a dash; you reply and reblog posts. But there's no significant word limit (it's upwards of a couple thousand words), and you can post either as text, chat, photo, link, video, audio, or quote. Also like Twitter, it's easy to change your URL/screen name, and because of the follow mechanism you can't easily reply to just anyone with just any muse (character). As a side effect, you're forced to focus on one muse at a time.
The difference between RP and writing is pretty significant, and cuts both ways. RP requires only that you understand one character, but it requires that you adapt that character to any situation. On LiveJournal, I too often got around this by picking the muse that had the reaction I wanted to write; on Tumblr, because it's difficult to change muses and reply to a conversation, I have to be able to handle one muse's reactions to anything that happens in a thread, or I can't reply.
RP is difficult in that respect, but again, you only have to have one muse's "voice" down pat. Writing, on the other hand, requires that you be able to juggle multiple characters' voices in one scene.
An RPer maintains a close-on third person POV in their head, watching for the most part through one person's eyes. A writer has to maintain an almost omniscient POV when writing, even if the only thing the reader will ever see is the POV of the narrator.
However, although writing requires significantly more investment in the characters, it's much more scripted. Even pantsers generally have some idea where they're going, or they know one scene they have to reach and write around it. Writers have the luxury of knowing (usually) where everyone will go and what they'll do ahead of time. Plotters like myself have this advantage far more than do pantsers, but pantsers have an advantage over RPers, who have no advance warning of what the other muse will do.
As such, sometimes I've had a muse both in a book and in RP. They require two very different skill sets, and allow me to go in-depth with the character at the same time that I build their world and their story. I know two people in my RP circle who do the same.
Today's question: When writing, how do you balance the limited viewpoint of your narrator with the omniscient viewpoint in your head? Or do you not have that viewpoint?