Well I have just bit the bullet and patched my main DAW.
I ran passmark before and after the patch and there was virtually no difference in the results for all categories, CPU, 2D GFX, 3D GFX, memory or Disk. In fact the disk result was 5% faster after the patch.
I then fired up a couple of Cubase 9.5Pro stress test projects which I made a while ago to exercise the machine and check for weaknesses. One has multiple large VSTi samplers, including 17 instances of Ivory with the largest sample sets all playing concurrently, the other with many, many VST fx. All still play perfectly after the patch, and I could not detect any difference in CPU performance since before the patch.
So from these initial tests, it appears there is nothing to fear from these patches. Considering these will be the initial rushed emergency patch, it is likely that they will if anything get even better when the vendors have had more time to analyse the situation fully.
I was fearful about these patches as only 2 weeks ago I got brand new kick butt hardware especially to run Cubase, and would not have been amused if my considerable investment had been somewhat curtailed. But it seems not to be the case, and I can detect no operational differences after the patch.
It seems that the worst affected people are servers and server farms, so hopefully Cubase users will continue to be OK.