Both of my campaigns are setup with "New" Amber players in mind, which means none of the starting characters known anything (or very little) about Amber, Shadow, or much else. No starting character has any Pattern (or Logrus) ability and therefore has no means of crossing Shadow (even if they knew what it was). Both starting scenarios therefore gather all the characters into one place, where the "truth" gets revealed.. how they accept that truth depends on exactly their chosen history and parentage. Once they have the ability to traverse Shadow (which they actually have to learn how to do, which leads to certain events, especially in the AiRP campaign) having the party split into different shadows at different time rates is something I expect to happen and in some cases is actually necessary to get things done. So this element is no more work than I would normally expect to have to do.. it's one reason why PBP (or forum) would work equally as well as online, and if I have players spread across the globe in different timezones would work better, since they could post their actions and interactions at their own convenience. The characters interacting with one another is actually a significant element of the AiRP campaign (given the setup) and may require little input on my part as GM. It's one of the problems I had with the last group I ran it with. most of them acted as they would in a stereotypical D&D campaign where because "joe was a dwarf fighter" that was all they needed to know about joe, which doesn't work for "joe" as an Amber character with a history they actually know nothing about.
I would also note in relation to my AiRP campaign, there are ways of characters starting with significant knowledge about Amber and Shadow and having the means to traverse them in a limited manner, but I'm not saying exactly how. One of my previous PCs (who as a player knew nothing about Amber) had this ability as does one of the NPCs. This is not as true in the Rodian War campaign..
I've put up a new thread on reddit/lfg_misc..