I believe I found the cause of my particular issue (and I don’t think it actually had anything to do with the driver pack I installed as mentioned above - but it’s possible it could have).
I’m using a surface book, and I went back into device manager, and my NVIDIA GeForce GPU was showing an error:
'Windows cannot use this hardware device because it has been prepared for “safe removal” but it has not been removed from the computer. (Code 47)
While this device was showing an error, I suffer the selection tool lag problem (activiating the selection tool freezes the entire program).
To fix Code 47 (on the Surface Book), I detached, and reattached the clipboard/screen (I didn’t reboot, log out or anything else, just detach/reattach).
After doing this, my NVIDIA GeForce GPU device stopped showing an error, and upon relaunching SU, the program was working correctly.
As a test, I issued a command to detach the screen through Windows (rather than the keyboard) and it put my NVIDIA GeForce GPU into error again (Windows is uninstalling this device. Code 21) - immediately SU was slow/unresponsive when using selection tool.
The device fixed itself from the Error Code 21, but the Code 47 required me to detach/reattch the clipboard monitor.
Again, this won’t be useful if you’re not on a surface book, but if you are, take a look at if that device is showing an error code.
I think when I applied the driver pack update mentioned in my original post, it likely forced the device to refresh and clear the code - making it look like the driver was the fix, when in reality, it was probably the fact that the device refreshed and became useable again.