Hey David,
If compositing for a movie, and your kit can handle it, I would always recommend going for the higher resolution. Depending on your editor, you may even do the compositing in 8K and reduce to 4K in the edit, to allow Zooms and Crops to be applied later.
But, if you are matching the highest resolution of the production, or the desired delivery format, then you should be OK.
With regard to frame-rates, then the production must somewhere along the way have decided this. Normally it is done before starting the shoot.
DCP Codec (or wrapper, some might call it) is something that the cinemas like most.
There are cinemas out there who will, at a cost, convert your ProRes or similar master file to a DCP.
Ultimately all of your questions are relied on what the producer(s) wants.
And, they are normally beholden to a customer, or specs from a distribution company.
Atb
Mads