I would like to be able to let friends connect from outside my house to stream media and allow them access so they can add films and the server goes off and finds them, extracts them, and adds them to the media server.
This is going to be the second most expensive part of this process (the first being storage). Direct streaming for one person can be done on anything that can play your chosen video quality. Streaming for other people will require at least a video card, and a processor that can handle multiple people, as well as the extra storage that other people will want to use. You can use a single pi4 for one person, but you’ll want to look at a desktop PC with a modern-ish graphics card (for the encode) if you want to share with other people.
I have the previous model. It does a great job of playing videos from my server in the other room. It technically can do YouTube, but that’s a pretty horrible experience. It can’t do any other paid streaming services.
But it does do an amazing job of local streaming. It handles most all of the audio and video codecs, and can direct stream just about any video file without too much playing around. I like mine, and definitely recommend it for anyone who also wants a trustworthy local media player.