CachyOS takes the default arch repos and re-builds packages targeting CPU generations and their instruction sets. There are no proprietary repos. Cachy has their own personal repo where some packages not in arch repos are built.
Gaming stuff is NOT installed by default, but there is a button in the Hello app new users can click that installs 2 meta packages that install almost everything one might want for gaming. Take a look at it in a VM and see for yourself.
The performance increases from their kernel + optimized packages are small but noticeable to me. Give their wiki a read-through:
https://wiki.cachyos.org/
Gaming stuff is NOT installed by default, but there is a button in the Hello app new users can click that installs 2 meta packages that install almost everything one might want for gaming. Take a look at it in a VM and see for yourself.
The performance increases from their kernel + optimized packages are small but noticeable to me. Give their wiki a read-through: https://wiki.cachyos.org/