does working on the pi offer you any automation / relief from the openwrt woes you had on the old router?

yeah, ansible works very well with raspbian, and just debian in general. openwrt uses like overlayfs and is very limited compared to a normal linux system, so although you could probably get ansible to work (it just needs ssh and python on the target system), it sounds like it'd be painful.

and why did you choose a compute module?

chip shortage, that was the only model i could get at the time. also the ethernet hat was like purpose-made for what i wanted a pi for.