I am not sure what makes a motherboard Linux-friendly... I guess fwupd integration with LVFS would be nice? Still, I am happy with my MSI B650 Tomahawk, since I can just put the latest firmware into an exFAT formatted thumb drive and update with it. All my laptops in the past had only supported firmware updates with Windows-only executables. I think I really should check out Framework for my next laptop.
While SteamOS is open-source and everyone can build one for themselves, it is only officially supported on Steam Deck. They promised to release a generic version of it targeting more devices in the past, and this post hints that that day is closer.
I don't see anything out of the ordinary. Pacman will warn you about those optional dependencies. But since you did not install them explicitly, there shouldn't be any problems. Packages listed next to grub are completely optional and do not break your bootloader whatsoever.
Edit: I tried to replicate what you had and it looks like you installed qemu (qemu-base is the default provider for qemu, the first one in the list when installing) and libguestfs explicitly. You should remove them with # pacman -Rs qemu-base libguestfs.
Pop!_OS uses systemd-boot bootloader by default. You can use T key and/or Shift+T key combination to change the timeout duration while the menu is on display. I have been using UKIs without a bootloader for a long time, but if I recall correctly you can reduce it to zero and have it be practically disabled.
Some games are designed with motion blur in mind. Elden Ring, for example, looks very unpleasant to me in 60 FPS without motion blur. But I disable it when using a mod that unlocks the FPS.
I have tried Bazzite before and understand its appeal. I am an ex-Arch user so I prefer the system to be as minimal as possible. Fedora fits my requirements just right and Bazzite does not seem to bring anything to the table that I miss from Fedora.
Fedora Kinoite. I like KDE, atomic distros and the fact that Fedora is the only (at least that I know of) distro that has proper SELinux implementation.
I also play games on this system, so having newer kernel and Mesa versions help.
In Aegis I can see an option for importing from Authy, but I looked up and I didn't a way to easily export from there. I guess that's what we get for using proprietary software. ¯(ツ)/¯
UFW, by default, blocks all incoming requests. This means that SSH (port 22) is blocked already. Then, if you need to, whitelist (ALLOW) ports that you want to expose to the network. For example, I have ports 1714-1764 whitelisted for KDE Connect and everything else is blocked.