Well to partially answer your questions - Fire tablets have the same OEM unlocking switch in their Developer Options. Just because that switch is there doesn't mean it can be unlocked! From a couple of videos I saw, the second option is sort of a manual OTA update.I'm thinking the same ! In the tablet Setting -> Developer Options, there are OEM unlocking (Allow the bootloader to be unlock) and DSU Loader (Load Dynamic System Update Image). Is this it?
There is the Screen Cast icon (which I like), but don't know how to use it. I have smart TV but searching the net all the talks were talking about Chromecast. Confused.