"Forgive me for asking yet MORE questions but...."
If there were no questions, beesource would just be arguments.
"If I split, add a queen excluder and stack, then set the new hive to the side (same level) just as the new queen is born, won't these bees exit high but want to enter low (which would be right back into the old hive?)"
I like the excluder because it seems to get more of a superceder response than emergency response; fewer better cells. I add a frame of brood to the queeenless side around a week in, do not know if I need to do that. With an excluder the workers go where they are needed.
The excluder stays in until the new queen is laying. Replace the excluder with a bottom then start to move the hives apart. Up to a month after laying is fine.
"Did I miss something? When I split and stack, should I have an upper entrance?
I do, but then I have one before. The upper entrance gets the top split field bees trained to using that enrtance, they stay with that entrance as you move it away.
This is not a high volume method, it is a low impact method that keeps a balanced hive. It works with only a few hives and does not require dedicated resources. The hive keeps on functioning as it would without the split. It does not have the drifting and robbing problems of normal splitting. Does not have the yields either.