144Hz should be fine so long as DSC is on.
Here is a proper list of resolutions/hz:
7680 x 4320 @ 60Hz (4:4:4) ( DSC )
7680 x 4320 @ 60Hz (4:2:0)
5120 x 2880 @ 60Hz (4:4:4)
5120 x 1440 @ 120Hz (4:4:4)
3840 x 2160 @ 144Hz (4:4:4)
3840 x 2160 @ 120Hz (4:4:4)
2560 x 1440 @ 144Hz (4:4:4)
2560 x 1440 @ 120Hz (4:4:4)
2048 × 2048 @ 60 Hz (4:4:4) (2K x 2K)
This is a red herring when it comes to the KVMs. Connecting a cable to the PC is not the same as connecting a cable through the KVM. This is because of how the KVM sees cables:
Importance of Length
Degrading Signal The more cable length and connections you have, the more the signal will degrade. You will lose a bit of signal through the KVM; there is no repeater in it. This is necessary because the KVM aspires to be a big dumb switch so it would not interfere with Nvidia G-Sync/AMD Freesync. This way you have fewer problems trying to use whatever hot new thing that hasn’t come out yet. Also, this helps us stick closer to the DP 1.4 raw specification without having to get creative.
Shorter Is Better!! So keeping the total run length from GPU to Monitor to about 10 feet (~3 meters) or less is important, especially for higher res/refresh. Certain combinations of equipment may require a 3+3 foot cable combination, for example. That’s a total length of about 6 feet, or roughly equivalent to what you’d have with a single cable.
How The KVM Sees Cables With this setup, your GPU sees one long signal corridor from the DP connector on the GPU all the way to the display. So a 6+3 foot cable is like as if you have about a 10-foot cable. Two 10-foot copper cables are not going to work.
Can you list what cables you’re using? How long are they?