As to the whether or not flatpaks and snaps are safe to install. Overall that are safe as long as you stick to the official repos, look over the description of the packages you want to install and don’t install anything that looks even a bit shady.

Why should I use snap?

Snap packages are much more secure than their non-snap counterparts. … Well auto-updates mean security issues are patched quickly but more importantly, snaps are isolated from the rest of your system. They have their own file system and can’t interfere with other apps on your machine.

What is snap software?

Snap is a software packaging and deployment system developed by Canonical for operating systems that use the Linux kernel. The packages, called snaps, and the tool for using them, snapd, work across a range of Linux distributions and allow upstream software developers to distribute their applications directly to users.