I would also prefer a larger, established distro. My #1 choice would be Debian with KDE, it is not a rolling distro but all my software and games worked on it. The only negative is that Plasma is very old and it's the version that had some annoying bugs that were fixed in later versions and I'd have to wait for Debian 14 to get that. But Debian support and stability are legendary. I run Debian on my servers.
So yeah, a rolling or semi-rolling distro may make more sense, maybe... so my second choice would be (semi-rolling) Fedora. It's noticeably not as stable as Debian, but it can be dealt with. The support is very good and they collaborate with KDE, even same devs work on both teams so it is the best distro for KDE. Though their ties to RedHat are both good and bad. Good, because they have access to RedHat's resources and engineers, bad because of the RedHat corporate influence. But if Debian gives me any trouble, I'll go with Fedora most likely.
I am not a big fan of anything Arch. Manjaro is probably the best derivative. Arch also has a growing problem with malware in AUR they can't seem to be able to curb; and it requires too much tinkering in general and I'm tired of tinkering with my OS, I just want to run apps and play games. I also dislike the snotty and elitist "I use Arch btw" Arch community. I would not want to be a part of that.
In my non-scientific testing I saw no speed benefit between any of the above. Debian feels more responsive though, but games ran the same. And all of them felt snappier and smoother than Windows 11
So Debian first, if not, then Fedora.
Oh, and I have NVIDIA and that means
pain on any Linux distro, even those with good NVIDIA drivers integrations like Cachy or Nobara. Considering current prices, I'm not buying any computer hardware this year and I would need a decent AMD GPU if I'm gonna do the switch. Or maybe NVIDIA cleans up their Linux act meantime.
PS. From what I see, Cachy's popularity does not really come from its claims of speed alone but to a large extent from the devs attitude and the OS design. Same as Nobara, they aim to make the OS friendly and easy for newcomers. They depart from the typical Linux "neckbeard attitude" that Linux must be hard and have a high barrier of entry. This is what Linux needs to become a viable desktop alternative to Windows and macOS. Along Valve, it's Nobara, Cachy and few other distros (Manjaro, Garuda, Zorin) that probably contributed to the noticeable uptick in Linux desktop adoption. Linux needs open minded devs like this. Sure, Microsoft's bullshit is probably the main reason, but these devs opened the doors to Linux for people who don't want to "have fun with their OS" and just want to do stuff and play games.
PS2. I finally found some Cachy OS vs. Windows 11 benchmarks. I don't know how reliable they are, I don't know any of these sites, so I'm not posting links. The general feel though is that if you have an AMD GPU then Cachy OS runs games at nearly Windows 11 speeds, but if you have NVIDIA GPU then Cachy OS performance is 20-30% worse than Windows 11. However, I saw someone run Nobara 42 (Fedora 42 derivative) against Windows 11 using NVIDIA GPU and they got similar 20-30% results. So not sure how much Cachy OS actually improves gaming.