(1) Take a snapshot of your current system (snapper+btrfs on Linux, bectl on FreeBSD+ZFS)
(2) Make destructive changes like install a new windows manager, some drivers etc.
(3) If everything worked out well, continue
(4) If something failed badly, restore from (1) using the snapshot restore -- Your system is as good as before
This workflow replicates many of the benefits of NixOS without the complex nix scripting that can be often needed.
Of course, a declarative and textual rendition of the configuration is better than bash commands entered on the command line but sometimes you don't need that level of precision.