Yeah, max jitter 113 with onboard card vs 1268 with discrete radeon. So, near golden onboard vs crappy discrete.
I would suggest to you using that machine just for for CNC work unless you are really interested in watching videos while your cutter is at work. Which wouldn't be the smartest thing to do, BTW. That radeon card could be better into another machine dedicated to, say, infotainment.
However I'm really surprised to see a so big difference. Usually I get better, not worse, performance with discrete cards, even if just slightly better. So, if the discrete card is really mightier than the integrated one, it could be that you need to set something either in your BIOS or in the graphics card kernel module. If you are willing to spend some more hours learning, there is good info about setting your radeon module here:
wiki.archlinux.org/title/ATI
wiki.archlinux.org/title/AMDGPU
I'm not really sure AMDGPU is privative or free. It seems to me that amdgpu is a new name for the old radeon free module, but I could be wrong. I have quite a bunch of old and also salvaged PCs but just one modern machine. You'd have to check it. You want to use the free module.
Here's the 4.19 kernel doc for amdgpu module, which lists all parameters available (please make sure you have the doc for the kernel version you are using):
www.kernel.org/doc/html/v4.19/gpu/amdgpu.html
That big bad difference could come from quite a bunch of things, I'm just speculating here:
It could be that BIOS is messing things up in some way, you should make sure the integrated card is disabled, etc, but I think this should be done automatically.
Perhaps that discrete card needs some firmware, you can check this with "sudo dmesg | grep -i firmware"
To see any warnings about that card, you could do "sudo dmesg | grep -i radeon" and "sudo dmesg | grep -i drm"
If you don't see any warnings on dmesg output, it could be something with your xorg configuration or kernel module settings. You shouldn't mess with any xorg.conf file, however. Usually the kernel does that work fine. Shouldn't that be the case, you'd be seeing something on dmesg output.
You could try some kernel boot parameters for radeon driver. Perhaps power management, video acceleration, pcie_gen2/3... dmesg output should give you clues about what's going on. You'd be on for some hours of linux graphics learning there, and it could make you feel really frustrated.
So, having almost fine latency with the integrated graphics card, again I suggest to you using that computer just for CNC work with the integrated graphics
