The Radio, TV and VHS tapes all work very similarly.
For the Radio or TV, either drop files straight into ch1 or ch2 (st1, st2 for radio) or just make any amount of new folders (named ch3, st3 and up) and drop them in there!
For VHS, make a new folder in tapes called tape1, tape2 and so on, and drop your file into there. VHS "technically" can have more than one file but there is no continuity check to keep it playing and it won't play in order. Tapes can have cover art! There's no size limit or requirements other than it has to be a PNG, but try and keep em similarily shaped to what the VHS should look like otherwise it'll stretch weird. Just drop 'top.png', 'side.png', 'front.png' and/or 'back.png' into the individual tape folder you made with the video in it and that's it!
If you don't want to have 100+ movie files in the game because, ya know, that takes up a lot of space, you can solely collect covers (Legally and on your own; I don't know laws on this stuff, so find them yourselves) and still make folders for them each and put them in there and it will generate a "blank" tape with that case. It will still act in game as a regular tape, you simply won't be able to watch it. Customers will still try and rent it, can be removed from case, etc.
If you name a TV channel or Radio station a higher number than you have actual folders, it'll create empty static stations in between to make up for it. This doesn't happen with VHS, but rather if you only have one folder named 'tape5', it'll internally call it 'tape1' because it's the only one it found, hence the naming convention.
There's no limit that I'm aware of to how many files you can put onto a station or channel and there's no limit to how many stations/channels/tapes you can have.
If you want to watch just a single file again and again, don't yap at me to turn on file looping or whatever, just put it on it's own channel/station and it'll loop. You can also put it onto a tape now f*** off.
Custom Video/Audio is passed through FFMPEG so it should be able to handle most file types, hardware depending.
***********HEVC, H265, 10bit or 4K video just shouldn't be used for performance reasons***********
In fact, during my own tests, I found that only until you get into larger file sizes for 1080p does it ever become an issue (20gb+) and even then, it's just a bit of audio de-sync. But 4k, 10bit video, HEVC, H265 whatever, they all crashed the game and I don't care enough to fix it. It works great as is.
For best results, I'd use video/audio files that have mono audio tracks. This will allow the 3D audio in game to work proper and is how the game is meant to be played. You can easily convert your own files using FFMPEG.