I am planning on pulling a frame of capped brood out of a feral/survivor hive I have that is doing well and letting them raise their own queen
they can't raise a queen from capped brood. you need eggs and small larvae.
i would probably give brood and combine at the same time. here is my reasoning: if they have laying workers, they will not try to make queen cells (probably). if they do not have laying workers, the brood should suppress the development of laying workers. raising a good queen takes numbers and good feeding. if you combine, you will have better numbers to bring in those resources. be sure to put your egg frame where it will be easy to check and mark it. in a few days you can check for queen cells and what you find will answer many of your questions.
if the numbers are still pretty low, you might want to give a frame of capped brood also to keep numbers up until you have a laying queen.
if you have laying workers, you should see brood...even though it will all end up being drone. it's usually scattered rather than the tight brood pattern that a queen will lay.
when you go into your hives look carefully at your brood numbers and patterns. look also to see what kind of stores they have and look for mites. there are other things that can take a hive down even if the queen is good. a queen may back off laying if there are not the resources to care for the brood.
as always, if you have questions and can get some good pictures, it helps a lot.