last year when I went back to Arch from Manjaro, I made a critical error. I'm not sure if I was just tired when partitioning things off or what. but I made my root only 20GB instead of the 50 that I had intended. I know in a lot use cases that'll be fine, but in mine, not so much. with steam compat taking up 1-2gb and keeping one version of pacman cache, I'm constantly getting the redline warning.
Tonight I plan on booting to live and resize my luks drive and hopefully not fuck it. and if I do? oh well...Timeshift will hopefully save me.
UPDATE
Booted to live and used gparted. had to fiddle with un-encrypting/re-encrypting the partitions in order to move everything around correctly, but everything was successful.
nothing ended up needing to be updated in boot. systemd-boot is so basic that so long as the uuids don't change, then it don't care.
All in all a good experience.