This page lists some things I have learned. If there are more things I ought to list, please message me!
POD in general (softcover, ebooks and audible):
Amazon is essentially a printer. You sign no contract with them. They have no rights to your intellectual property. The only thing you can’t take with you is a free CS ISBN, if you choose to use one of those. I believe the Kindle Select does ask for a three month exclusivity.
Hardcover is available through Createspace Enterprise but only for Authors, not for general distribution through Amazon. In other words, you can order a thousand copies, but sell them elsewhere, not on Amazon. It costs $100 to set up.
In general the price for POD is around twice that of printing a thousand together, but there is no outlay.