I don't use either but IMO people are far too worried about bloat, it's not some monster that'll drag you down. Unless you're extremely space constrained some extra packages on disk won't make any difference. And even on the slimmest install there'll be stuff you never use anyway.

Don't buy into the bloat meme.

I use Arch on all my systems now. It does great for gaming on both my beefy gaming PC and my little work laptop (within their respective punching weights). I haven't felt the need to explore CachyOS or any other variants for performance gains and I really do appreciate how bare bones Arch is. Just having the lightweight OS that isn't doing a darn thing beyond what I've asked it to claws back plenty of performance, although I'm speaking more in contrast to Windows than other distros having any sort of bloat.

Still, Arch has been the first distro I really committed to, I've been on it for a year and a half now and learning how to build it out taught me a lot about Linux.

Also, I'm just never sure how long some of this offshoot distros will hold on for, you know? Is that unfounded?

Start by using base arch and eventually you can try to use the cachyos repos if you want to try and get some performance uplift.

I suggest installing EndeavourOS because it is pretty minimal, you can even select the option to not include EOS's OS theming during the install process, so basically a bare install. Their installer also allows me to choose ext4 instead of the buggy BTRFS file structure. Then, after install and updating, I add the Chaotic-Aur repos. and do an update. Then I get the Garuda Linux repos installed. Why? Because they have lots of handy tools, gaming, power-daemen for both performance and power-savings (laptops) and a handy app for installing kernels, including the CachyOS kernels and their optimizations in the Garuda Settings Manager. If you don't want ext4 file structure you can skip EOS/Chaotic-Aur and just download Garuda KDE light edition.

Else, get Garuda repos on your system by downloading 'Garuda-update' from here, and install with Octopi or CLI command, and then do a system update, then do 'garuda-update' in terminal which should pull in the garuda repos (say 'yes' when prompted to all the options to add repos.) Minimal system with lots of options to choose.

I've been seeing a lot of people pushing catchyos lately. Has anyone actually tested if these optimizations actually offer any real world benefit?

I have been an Arch user for a decade. This year I switched to CachyOS to give it a go. Performance (for me at least) has indeed improved but its not a massive jump.

I don't find it particularly 'bloated'. There wasn't much I had to uninstall after installation and the installer gives you the option to deselect packages. List of packages here: https://github.com/CachyOS/cachyos-calamares/blob/cachyos-systemd-qt6/src/modules/netinstall/netinstall.yaml

Its also not as simple as many people claim to switch to CachyOS just by changing repos. CachyOS also has some of its own configs that would also need to be imported. I found it was easier just to install Cachy and remove unwanted packahes than switch repos on my Arch install and fiddle around with a bunch of configs and change some packages and settings.

So far I have found CachyOS a little more buggy than my install of Arch. But not so much that I want to switch back. So far the slight performance increases are keeping it worth it.

If, gods forbid, CachyOS ever stopped being maintained, it will be easy to switch back to vanilla Arch.

You can try Endeavour OS. Its pretty close to stock. I found cachyos was too bloated for my likings and ffmpeg ran faster on EOS than COS in my case.

Install your own from one of the parent distros: Debian, Fedora/openSUSE, sources (eg. Exherbo, Gentoo), the state-based one I always forget.