I think you're unnecessarilly restricting yourself by a wanting a full disk btrfs, particularly if you want to use UEFI or hibernation.. why do you want to restrict yourself in such a way?One tip I can offer is to disable compression on your /boot subvolume. And disable COW on your /var/log directory.
Fix these.https://bugs.archlinux.org/Or contribute to the wiki. Or seed the latest iso torrent. Or rewrite a popular, yet slow, application in pure C and submitit to the AUR. Or Help out with user problems in and around the forum, etc.
Do you really want these things to start at boot, or do you want them to start when you log in? If you want them to be run at boot, read this: https://wiki.archlinux.org/index.php/Sy … process.3FIf you want to start something when you log in, refer to your DE's documentation, or use .xinitrc.