I think I can tackle #3: Bryce lightning can do single frames. Instead of telling the thing to do a bunch of frames, have it do just 1.. that will be the current scene. Read the Readme file for lightning incase there's a problem, and the help manual is good to get started.

#2, I am not sure because I have not wondered about it myself. I would think no because it's not in view. Lots of my stuff have junk off the side which are not in the scene. Doesn't seem to impact the time. It still takes up memory, though, and that itself could be a burden.. but that's a different scope of issues.

#1, the way I do it is without a particular method. I usually start off with what is close to the camera first then work my way outward. The reason is the wireframe can sometimes be a problem when selecting small objects. Sometimes, like with trees, the mouse will miss a solid part of the tree and get the background mountain. On large complex scenes, it's usually easier for me to have more than one file. A file for background stuff. A file for close up stuff. A file for middle stuff. Then when they are all ready, I'll merge them all into one scene for the final render.