The standard version of Linux mint is with Cinnamon. Desktop environments are basically how your desktop looks. Cinnamon looks similar to Windows, and Mint is newbie friendly, so you will have no problem moving.
A lot of us understand that if you type anything in a computer it is assumed to be on the public record either easily found or through a few hoops to get it.
The problem is that nowadays your medical documentation, banking and other sensitive data is all transferred through a computer.
And it should be protected and private.
If you don't want to change anything major in your phone or go into the technical stuff, iPhone is better, but the best phone privacy-wise is a Pixel with custom (privacy oriented) ROM installed, since Pixels have the best security features among Android.
You can install an apps which basically display the WhatsApp webpage like an app, if you use flathub at least