I first make sure i have a fixed white balance in the various PTZ camera's in the project before messing with the whitebalance \ color optimizations in vMix.
PTZ camera's can be limited in the color optimizations so vMix can help you to get various brands\types in line in your project.

Agree 100% with Joeboe69.

It's always best to get it right "in camera" whenever possible, for a variety of reasons.

Exposure and white balance adjustments are better done in camera because once it goes out the HDMI port from the camera to the computer, it's converted to 8-bit color, and making adjustments downstream won't be as high quality.

Some features of vMix work better with raw camera feeds, and not processed feeds. Instance replay and multirecording come to mind. Yes you can assign camera feeds to Outputs, and then use the Outputs as sources to instant replay and multirecording, but you have a limited number of Outputs. And multirecording isn't stable when recording from Outputs, in my experience.

The above also applies to framing and cropping. You can do it in vMix, but the above point of raw camera feeds vs Outputs also applies to changes made in the Position tab for inputs.

So, in short, do it in camera when possible. :)