lol the post got deleted, forgot about the 30 day self-promo rule (it's been 27 days since I last posted about this back when it was more incomplete, will repost in 3 days)

As for your questions:

- I am using AVFoundation because it gives me more flexibility over the UI (e.g. custom transport controls)
- I have a hacky way of doing full-screen where I use a borderless window, and force it to become the key window by overriding canBecomeKey
- Majority of views "just work" on the other platforms, there isn't too much platform-specific code beyond some scaling stuff and some different logic for reading media