Microsoft only has your key if you give it to them for convenience (by syncing to your Microsoft account), and they’re required by law to give anything stored in their servers if asked. There’s no conspiracy here.
If board partners now provide their own VRAM, maybe they will provide more memory configurations for GPUs instead of the ones NVIDIA forces you to have.
That’s your definition of a developer kit. For Apple, it’s a device that allows developers to test their Augmented Reality apps in the Apple ecosystem. They market it for people because it helps pay for R&D, but this is obviously not the product they want to sell.
I use MediaMTX. You can stream to it with whatever (I use OBS). You could even publish it to a website behind an iframe.