Righ, slowroll is just a different cadence of package versions, and it just switches to slowroll repos. As for whether the packages will downgrade, I would guess yes. This is because Slowroll takes the same approach as Tumbleweed, where each release is a snapshot of a configuration consisting of packages of a specific version that are known (to the best of the maintainers' ability) to work together. So they will likely downgrade to match the known good configuration.
Unless you crossed a major new feature release in Tumbleweed that hasn't made it to slowroll, I'd say that's probably not an issue.
My understanding is that slowroll is just tumbleweed with more stringent release criteria. Looks like the Agama installer for it might be missing systemdboot, but since you are migrating from Tumbleweed you won't be using that (its just a repo switch rather than a new install). So you should be good to migrate right now.
I have always been advised by the "greybeards" in the openSUSE community to always use zypper dup with Tumbleweed. This is because doing so ensures your package environment is always in line with what was release on openQA, ensuring you are covered by that quality check. The language is in this link is probably confusing and should be corrected; its probably more accurate for openSUSE Leap.
I would recommend removing PackageKit and always using zypper dup with Tumbleweed, and that's what I do.
Yes, there are apparently some different scenarios (perhaps DRM? I forget) where the non-free codecs in Packman are better. I would install them, just be aware when you do zypper dup that Packman will often lag behind other repos in the version number and you should choose the option "keep obsolete" when resolving the conflict, otherwise you'll end up with a mix of codecs from the openSUSE repos and from Packman.
Remember that a rolling distro is bleeding edge. That means that from time to time you WILL encounter some issues.
Tumbleweed is (somewhat) unique in its approach to rolling. The quality checks that occur on openQA partially mitigate failures by withholding the next distro upgrades until they can be reviewed. However, the openSUSE devs are not perfect, openQA is not perfect, and some times rolling forward with a known issues is deemed acceptable.
This is where btrfs comes in. The answer to your question of what to do if zypper dup fails is two part: A) roll back to the automatic "pre" snapshot taken by snapper before the dup. B) Just wait for the devs to fix the issue!
If you are impatient, you can check for progress on a specific issue by searching the issue on https://bugzilla.opensuse.org/, or chat up the community either on the forums or on the matrix space in the support room.
Even "in universe" content might be a way to bridge revenue between ME and the next franchise if they've run out of ideas. Star Wars has made an insanely successful business taking "background" characters or events and expanding on them. To be honest in my opinion those constitute some of the best Star Wars IP, whereas attempts to return to the "main storyline" (Jedi vs Sith) kinda suck.
Personally I'd love to see a deeper dive into Cerberus. Depending on your ME3 crew comp and romance options they sometimes just didn't seem very relevant to the endgame, or really have much purpose other than the storytelling device used to justify Shepherd still being alive.
Even a look into the previous experiences of the crew would be cool, which is fairly simple given they were all given relatively rich backstory to fill out dialogue.
But I 100% agree the main story should end, especially after Andromeda already provided a look into the future of the Galaxy post-Reapers.
Take a look here, it explains more about the specific configuration, such as which subvolumes are automatically snapshotted and include in rollbacks, bootloader integration, etc
https://doc.opensuse.org/documentation/tumbleweed/snapper/
Basically there are many details in the setup of btrfs that are needed to get to that level where you can be confident of being able to easily rollback to a previous state. After losing some data on a manually configured btrfs setup on Fedora I went to openSUSE specifically because they have already done all the hard work for you on the btrfs config
Netmaker is crap compared to Netbird unless you really need nodes to connect with native wireguard. Netbird has better ACLs setup, clearer documentation, and even has a new reverse proxy feature
This is what openSUSE Tumbleweed is designed to do, although config files in /home require manual setup to include. It allows you to completely rollback if necessary after a system upgrade, allowing you to use a bleeding edge distro without fear of having an unusuable system. If an upgrade goes bad, usual procedure is to roll back to the last btrfs snapshot and just wait for the fix (which usually comes in a couple days to a week, as Tumbleweed advances rather quickly).
openSUSE has a specific btrfs subvolume setup and grub/systemd-boot integration to enable this, which is not too common even today, so it really is a bit special in that you can have this functionality without excessive time spent setting it up manually.
Actually not bad advice if they are into you badly speaking their language to them at first 😂