A:Answer The Kindle is not able to work on Bluetooth for connectivity, but can for audio.
All models work on 2.4 GHz.
If a version has 4G it can use the Cellular network in place of Wi-Fi, For an extra cost.
Early units had something called Whispernet.
This was a free Cellular connection, but most of those models are not not able to function as they can not run the current firmware to connect to Amazon to get your books.
I thing, unless you need 4G or waterproof, the Kindle 2019 version it the best bang for the buck.
If you travel a lot (me) and like to sit in a hot tub in the evening and need a waterproof version the Oasis it the one for you.
If you just need to be able to have access to the internet without tethering to your phone or local Wi-Fi then a PaperWhite 4 with 4G (extra cost) is for you.
Please look at this web page for details of features.
https://www.the-ebook-reader.com/kindle-comparison.html