Void on a ZFS Root. It has a 13 year old budget laptop CPU and a very slow HDD.
But it is snappy and it uses less RAM than Xubuntu and Mageia + XFCE.
It is unbelievable that this kind of super recent kernel works so flawlessly on 13 year old hardware.
NixOS is an awesome piece of software.
At 86,180 packages, of which 80.7% are the newest version, NixOS has both one of the largest sets of packages and the most up-to-date (second to none).
It also has high performance. NixOS is almost as fast as FreeBSD and Clear Linux in the most realistic benchmarks. It is faster than 90% of Linux distributions.