So I tried it on an old Pi2B and my zero W. There is noticable delays across network (running nothing but plex media server off Pi2B was super slow; using zero for my pi.hole, granted the pihole hasn’t been too much trouble.)
I used to run plex off the Pi2B with Raspbian Lite, and had a much greater performance - connected via Ethernet to my router, and Smart TV other WIFI. Never had a problem with buffering before.
While it also took a few goes getting dietpi to take on the Pi’s, I like the dietpi.txt file can be configured straight off the bat (made the zero almost instantaneous).
I don’t think I’m sold on it. Going to give it another week before I pull the plug and go back to raspbian lite.