I've been having an issue of lag in every CC version of Photoshop. This has not been located to one computer but 4 different computers over the last 4 years have had the same issue, and these have been very high end machines that have no problem with After Effects, Premiere, C4D, etc.
Mainly, the clone stamping tool and healing brush tool have lag when sampling. I was advised to turn off "Show Overlay" in clone source and that helps; however, I don't understand why CS6 does not have this problem (while also being able to show an overlay with the clone and healing brush) and these newer version can't use "show overlay" without lag. This has been an issue since 2017 and I recently caught the "show overlay" fix since it was only posted about in 2020.
There is also slight lag when togging a layer on and off. I do retouching so I am frequently using a hot key to show/hide layer. It works fine 70% of the time and then there is that 30% where I toggle the show/hide and it doesn't catch it and I have to do it two or three times before it catches up. Again, this was never an issue in CS6.
I recently tried 2021 thinking the issue may have gotten better but 2021 is even worse. Turning off "show overlay" doesn't even seem to speed up the brush anymore.
Please let me know if there is a fix, or if this is a known problem and it is being worked on. I continue to work in CS6 because it is still the version that performs the best. I have not run into a single issue in CS6.
I'm currently using:
Windows 10 | i7-8700k @ 3.70 GHz | 32 gigs of RAM | NVIDIA GeForce GTX 1080 Ti with the latest studio update.