Well, I like Fedora more than openSUSE but I can’t tell you why. It is just my personal preference, because I believe that on Fedora, one is still a bit closer to the Arch-like word with lots of freedom, while openSUSE feels like a lot is “already maintained”. You should try both.
If you are not planning to use applications that heavily rely on the underlying system, such as the texlive distro, or lilypond, or something similar, then you should be fine with applications installed from flatpaks and you could enjoy the perks of an immutable system with its easy updates and upgrades.
You could still use Silverblue with texlive, but it sometimes requires to run them in toolbox.
I do not know, the only thing I have always wanted to be restored are the personal data. When my system crashes and I need to reinstall (which actually only happened once when I made my own mistake that corrupted the entire DNF database), I reinstall, copy the data and just start using the system. If an application is missing, I will install it as I go, which helps the OS from getting overbloated that much. From the Fedora perspective, there has not been an issue so big since Fedora 24 when I would need to reinstall the system from scratch.
On Fedora, you can easily install other desktop environments on top of any original desktop environment, so using the Spins is (as far as I know) just cosmetics. The spins use various tools to provide the functionality, so they might look different or use different applications. If you are new to Fedora, I would start with Fedora Workstation (Gnome), or KDE, because these two variants get the most attention and testing with Gnome being even more tested than KDE.
You can install any other desktop environment on top of Fedora Workstation according to your likings.
PipeWire → if you are into music, PipeWire provides wonderful routing options, latency and audio handling. In Fedora, this is a default solution and it provides good enough results for musical production as is. No need to tweak terribly.
Newest Gnome with each new versions.
RPMfusion → a repository with lots of packages that cannot be part of Fedora for various reasons, well maintained, compatible without issues.
Flatpaks → the flatpak system installed by default, you can install many applications provided as flatpaks.
Programming languages → lots of programming languages that you can install from the repositories: newest Python releases, many Perl packages available, etc.
The thru reason we have spins is, that we can test the different DE’s as a live system on the computer. And if we know which works best for us we can install it too.
Of course it is possible to install everything on the workstation installation. Just be careful if you remove software. Sometimes the software removes dependencies from the other DE and you will have a broken additional Destop Eenvironment.
You can test this on a Workstation too. Toolbox is a other/same version of fedora/RH as a container just so that you can install software in it. So you have, while the base system is immutable (in Silverblue), the possibility to install additional software/environments.
I will say that both Fedora and OpenSUSE are great Linux distributions (I’ve used and written textbooks on both). But it sounds like you want to find a long-term distribution, and much like buying a house, you want to be sure it’s a good fit so that you don’t have to switch later.
In your case, might I suggest running both for a week or two? Perhaps in a dual boot configuration, or within virtual machines? I think that if you do that, you’ll be able to clearly see which one you prefer, as well as be comfortable with that decision.
If you want Gnome to look like KDE, then you need extensions. If you learn to use Gnome as it is by default, then it is not bloated at all and actually pretty fast, too. Do not let yourself go astray by trying to achieve what others have already achieved. Try to explore the unknown.
How is Gnome preventing you from multitasking more than KDE?
It is actually very good for multitasking, I believe. Not only you have virtual desktops, where you can group applications to suit your workflows, but you can also tile applications to the left and right to be able to see even more. There are bunch of shortcuts to switch between applications, desktops, etc. The only thing that I tried and that was even better for multitasking was a whole tiling desktop, such as Sway or ID3.
Try it out for a couple of days and then make your decisions.
The suggestion to try different spins from the live images makes it quite possible to test what works for you.
The suggestion to try things in a VM is even more viable since the VM can be fully updated just as if it were installed bare metal and one can test the latest software updates as well. (many packages and kernel upgrades have been done since the F38 release in April.)
Whatever you have installed now, I would suggest that you try others in a VM installed there. If that is not possible, then install fedora workstation, add libvirt and virt-manager, then one can easily install different spins into different VMs for comparison as they make their decision as to which is best for long term use.
Don’t get “hung up” on the question of containers, they are easily considered light weight VM’s in some respects. When you think of Silverblue, you can easily do pretty much the same thing you can with Workstation, all while having pretty stable system level changes come down to you.
As for OpenSuse or Fedora I believe Fedora has a different release cadence and even different project goal than OpenSuse. Both are based on GNU Linux so there are similarities.
Snaps can be run on Fedora, though I don’t use them so you should search here because the question has come up more than once. Beside flatpaks are superior.