My research into the connectors has given me this information so far:
I think most of the ATX MiniFit jr connectors are specified (a new consolidated series i think,) in this:
https://www.molex.com/pdm_docs/sd/039039242_sd.pdf
[Molex brand part numbers for black connectors] (pn / mfg eng pn)
ATX 24 Pin Connector (Female) single piece:
39-03-9242 / 5557-24R-400
EPS (cpu) 8 Pin connector (Female) single piece:
39-03-9082 / 5557-08R-400
EPS (cpu) 4 Pin connector (Female) single piece:
39-03-9042 / 5557-04R-400
[Molex brand part numbers for black connectors, for Seasonic Focus Platinum 750w]
Seasonic Focus Platinum 18 pin (Female) psu side of 24pin:
39-03-9182 / 5557-18R-400
Seasonic Focus Platinum 10 pin (Female) psu side of 24pin:
39-03-9102 / 5557-10R-400
PCIe 8 Pin Connector (Female) single piece:
45587-0004, (3rd generation polarization) Referenced in sheet for 45587-0003, page 2, right hand side
https://www.molex.com/pdm_docs/sd/455870003_sd.pdf
PCIe 6 Pin Connector (Female):
45559-0002, sheet:
https://www.molex.com/pdm_docs/sd/455590002_sd.pdf
Unfortunately, I have not found the 8-pin PCIe part on Mouser, Allied, Digikey, or Newark. Mouser is talking to distributors for me, but I have not heard back yet. I was hoping to make my own psu cables and needed these connectors, but have not been able to find them through the usual suppliers. I might have to check mod sites, but didn't want to pay $5 each for a no-name brand. Some of these connectors are still available under older part numbers, but I have been collecting the information for the newer part numbers to keep it accurate going forward.
hope someone finds this useful.