A place to start would be:
https://www.crucial.com/upgrades
After that, you do not HAVE to buy a crucial drive, but that may indicate SATA III, NVMe, or both.
I would expect most current AV receivers take USB as an input.
I know my 5 year old Sony STR-DN1080 does.
https://electronics.sony.com/audio/audio-components/av-receivers/p/strdn1080
Not even a little bit. I rely on the AI bots not at all.
As regards phone vs PC/laptop use...also not even. My phone use is so minimal as to not exist at all.
googling for 'photo to cartoon'....
https://www.befunky.com/features/photo-to-cartoon/
https://www.fotor.com/features/photo-to-cartoon/
https://play.google.com/store/apps/details?id=com.vicman.toonmeapp&hl=en_US
https://www.cartoonize.net/
There are others