Does this include the 5300 and 6300 Performas? The Quadra/LC 630? I'm working on a big index of CPU upgrades and I need more info on those machines.
Yes. Any 63xx
before the 6360 was basically a "fixed" (depending on how you see it and who you ask) x2xx Performa
Others have answered on the 040-to-PowerPC front, but were it me, I would leave it as an 040 machine. There is this resource to bump you up to the "max" 40MHz, but it requires SMD component prowess to not !@#$ up your logic board.
http://www.applefool.com/clockchipping/q630.html
My 6214 board does have a regulator on the board, but I can't tell whether or not it's 3.3V
You would need to check everything very carefully. While this is
not a 1:1 upgrade guide, this is a good reference on what needs to happen when modifying these "backplane" style Macs
https://powercc.org/takky/ again, this is
not a step-by-step, but more of a reference. It's meant for 030 "backplane" Macs.
I don't know for sure, but my guess is that it isn't. A 3.3V rail was really only needed and added for PCI Macs—it's the reason it exists on the 6360, x400, and x500 Macs of the era going forward. Most other Macs you'll see 12V and 5V, but again, my knowledge on the topic isn't exhaustive.