Okay, I have fairly conclusive data to report and will get more in-depth when I can.
Tested on a dead forum first and the site went from noticeable latency to like I was pulling from my hard drive. Did the edits in this download.
https://vborg.vbsupport.ru/showthread.php?t=201211
At midnight last night switch DNS from Cloudflare to Google Page Speed on a massive, busy forum (1200 simultaneous users). Intended to test overnight but DNS propagation is taking over 11 hours now and is finally starting to reflect that we're on Google's servers. A scattering of members are initially reporting oddities and being logged out but no major outcry.
I will report back. I recommend you do the Page Speed test and decide from there.