MuPDF is good for books and comics, KOReader is better but it takes time to learn it. I would get a big SD card, download movies/books/stuff on pc and just transfer them using SMB/(S)FTP/USB.
What about sending a big-ass zip with your playlist inside?
I’ll help you, dm me.
While i would sate that in a slightly different way i do agree with you, also i recommend you to remove word these, it would enhance quality of this statement.
You can try YT music via piped.