You know, when I first migrated from Poser to DS, the UI in DS 4 drove me nuts. I will admit it was a difficult transition in the beginning. But the more I worked in DS, the more comfortable I got with it, and then I got to really appreciate the layered/tabbed style. And now when I'm in Poser, the Poser UI makes me pull my hair out, because it's so dang CLUTTERED. LOL
So, I can totally understand the difficulty adjusting to the interface. The two UIs are very, very different.
As far as the wide screen layouts for something like your Last Supper series... the bulk of the posing has to be done with the scene in view, I know. I do stuff like this all the time for my renders, and I have found that I just get into a habit of working with the "whole scene" for the bulk of the posing, then switching to a posing camera to do the more minute things like hands that are touching another figure's body, or positioning fingers just-so.... then I go back out to the main view with the whole scene to resume the rest of the posing.
Basically, I use the "posing camera" thing in DS to do the fine tuning on small parts of things, and I do the majority of my posing with the "full view" in my scene window. Don't know if that helps you any or not, but that's how my workflow has developed over time with Studio.