Debian is Debian based and regular Mint is Ubuntu LTS based and use theirs respective repos (not a big difference for the average user). While currently the non Debian version is the main and recommended version, due some controversial changes in Ubuntu people want to move away from Ubuntu and the devs have considered making the Debian edition the main one.
Snaps is Ubuntu/Canonicals proprietary package format which is mostly considered a worse alternative to flatpak (another package format) with no real advantages on desktops that Canonical is trying to force on users
I don’t like WhatsApp, but some people simply refuse to use anything else (“better”) and the web clients can bridge the gap but it’s extremely annoying not being able to answer a call with a person you are texting