You might consider Shelly I guess which the Cachy team is actively contributing to. Or Octopi which is more established. Or maybevthe cachyos-update?
I don’t use any of these so can’t comment on their suitability for your purpose.
It’s a tight size, especially with frequent updates. Maybe consider Maclean? Even just your pacman cache could easily be half the space used.
Snapshots only contain data which has since changed, so normally they would grow quite slowly as changes in your system build up.