Wanted to add that for Ingram Spark, I believe if you just do a print version first, you can keep editing without paying the revision fee because you get a chance to sign off on the proofs each time, refusing to do so can give you another chance to upload a file. The eBook version goes up instantly once you've approved it. Revising after that is what dings you with the fee.
I don't know if this is still possible, originally we released the print version of a Children's book and added the ebook months rather than do both at the same time (as you mentioned, they are weird formats to wrap your heads around so we needed the extra time.)
This was before Ingram Spark changed their UI so unsure if you have to do all the files at one time.
For colour quality, the standard wasn't too bad and is half the cost of the premium (which really shoots up the unit cost).
Hope adding that is of some help to people.
We quietly released our comic after originally having it set for May 2020. All shows were cancelled at that point but we'll figure it out when the world opens again.