So far as I'm aware, there are four versions on the market right now:
- Corsair RMe which comes bundled with a cable that uses 2x PCIE ports to make a 12VHWPR connector. This is a lower standard of unit compared to the RMx PSUs and has a 7 year warranty.
- Corsair RMx original version (pre ATX 3.x/PCIE 5).
- Corsair RMx SHIFT, which is now an updated ATX 3.1 PSU with side-mounted cables (and limited case compatibility).
- Corsair RMx ATX 3.1 version, which uses a dedicated port on the PSU for the 12v2x6 connector.
So, to answer your question: I wouldn't get the RMe unless it was particularly cheap.
The rest doesn't matter unless you're planning to use an nvidia card (4070 Super or higher, most 4070 and below still use a PCIE 8 pin connector).
I'm not aware of any new Corsair HX PSUs.
In terms of which is better from the RMx, RMx SHIFT and RMx ATX 3.1, I have no idea.