I can't answer either of your questions, but you might want to make the second question a new thread. It has been discussed some on Discord and form my brief skim, it looks like the new API is something developers can use for individual apps. Not clear why they would or what pressure Google might apply to have them do it, but it doesn't yet seem to be "you can't sideload anything" and I suspect, using mostly older apps, it won't present a big problem to me, but I really don't know. It's a good question, if anyone here knows.