Do you need Timeshift on an opensuse system? I haven’t used Leap, but had a Tumbleweed install for years which has Snapper pre installed.
You can install btrfs-assistant to help you manage snapper. You could have it create backups of your /home, then you can rollback if you think you’ve messed up too much.
The firefox thing seems just firefox behaviour to me. Does it not do that in Windows? But you could use a firefox based browser that respects privacy more. Librewolf and zen browser you can install via Flathub or an appimage from their website. Librewolf at least will by default end and forget a session when you close the browser.
(FYI - best way to deal with appimages is to install Gearlever from flathub, then when you download an appimage you open gearlever and “install” the appimage. Gearlever is just for better integrating appimages into your system but also for keeping them updated).
My last Tumbleweed install I ran from 2019 to 2023. During this time flatpaks got a lot better and flathub got a lot more programs available. Now I use flatpaks as my first option for software, unless I think it’s something that will give me problems being containerised.
Opensuse 1-click… you’re right, those can be a pain. You often end up adding additional repos, and it’s never fun trying to clean up the problems that come with that after a while.
My suggestion is search for “opensuse ‘programs name’” and see if they maintain it in their repository first. (You can use Opensuse’s preinstalled Yast to search for it even to keep it simple). If no, look for it on flathub, remember to look to see when the flatpak was last built, in case it’s been unmaintained for a while. Failing that, check the developers page (usually GitHub or gitlab or similar) to see if they have recommended steps for install.
If the Firefox thing is a real pain, do consider the librewolf project, since it won’t save your session every time, but also has ublock origin already set up by default.
Remember that even if you’re unsure some software is for you or not, just try the flatpak. One command to install, and one command to remove if you didn’t like it. Because it’s containerised you don’t need to worry about it leaving behind unused libraries or cluttering your system with leftover bits.