Advice on RAM upgrade (3600MT/s DDR4)

[itm]

I want to increase (ideally double) the RAM on my Proxmox host. It runs on a Ryzen 7 5700G / MSI B550M Pro-VDH. Current RAM is Kingston Fury Beast 64GB (2x32GB) 3600MT/s DDR4:
*no competitor links*
...but this is now discontinued.

Can anyone recommend alternative 2x32GB RAM modules, as I'm confused between the MT/s and MHz speed ratings. Most outlets quote speed in MHz, so for example can I use any DDR4 3600Mhz RAM in parallel with my two existing 3600MT/s modules?

I will probably also look for second-hand RAM to keep the costs down.

 

[itm]

So would this be fine alongside my existing RAM, for example?
Corsair Vengeance LPX (Low Profile) DDR4 64GB RAM (2x32GB, 3600MHz)

 

[itm]

fine is a relative term
in theory, yes it should
BUT
running 128GB of ram at 3600 is an EXTREMELY TOUGH ask for the memory controller
i would not be surprised if any of the below applies:
1) you couldn't
or
2) will need to run at reduced frequencies/slower timings to get it to run without errors, and/or
3) bump up the CPU IMC voltages (maybe to potentially unsafe levels)

Oh OK. So what would be the upper limit of RAM that could comfortably run at 3600?