A drive like the Patriot Memory P400 Lite is very low power, so it works with cheaper enclosures or USB ports that don't deliver as much power to the peripheral. It also generates less heat, which can help sustain performance depending on the enclosure and environment.
ext4 can't be natively mounted in Mac and Windows but you can install third party software and still mount it from the command line easily. And of course ext4 works fine with Linux natively.
I don't know if you can install the Mac OS or Windows OS on an ext4 drive and directly boot from it, however.
Linux has FUSE read-only support for decrypting APFS. iOS can read/write encrypted APFS that is formatted on macOS.
Would be nice to have encrypted ZFS support on multiple platforms, including iOS and Android.
If you don't need to use it on Mac/Windows, use a FS like BTRFS with checksumming feature.
Don't use any FS that doesn't have checksum feature as silent bitrot is real.
I have had Wikipedia on my phone for years, local search is fast enough. I also recommend Wiktionary, which has practically every word in every language and is less than 10GB.