To give you a bit more detailed information:
For 1080p YouTube has a maximum bitrate of around 8mbit (although, it can go significantly lower and still be acceptable).
So, 16mbit will be plenty.
For 4k (which I understand you don’t care about but just for completeness) can theoretically go up to around 40mbit/s, but in reality I’ve very rarely seen anything beyond about 25mbit.
With 16 Mbit you would struggle to do consistent and good looking 4k.
If you have a HDR screen and want HDR content, you need to essentially double the bitrate, meaning that you can just barely support the best quality HDR 1080p content on YouTube.
Other streaming services follow similar numbers, but most services stream on a lower bitrate than YouTube, so it should work just as smooth or smoother (although obviously at lower quality)
You were unable to understand how he gets the phones, despite him explaining it. That makes me think it’s some weird complicated scheme, that is “sort of legal” or “appears legal” but really isn’t.
Most of the time these sort of schemes are based on cancelling a contract, but never returning the phones. Usually require someone internal who can essentially remove or cancel orders after they have been shipped. It’s a pretty common scam, that usually works for a good amount of time, until the seller does an inventory and realize they have a lot fewer phones than they should.
Why would a scammer give you the money back? Cause he wasn’t trying to scam you, he thought that he had successfully scammed amazon, and when it turns out that Amazon have realized that something is wrong, he really, REALLY want you to not talk to police about it, hoping that Amazon only know that someone has stolen the phones, but not who has stolen them.