So , slight cross -over in terminology.
The osd in the VTX you have displays volts and that on your video feed.
Very handy as you don't want to run your batteries too low.
When I referred to a camera with osd , I should really have said " camera with adjustable parameters "
Such a camera will have a small "select -up-down - left -right " widget that plugs into camera for making adjustments .
The parameters being adjusted will be displayed on your goggles / groundstation - hence , whilst widget is connected , they are displayed-on-screen.
Widget usually removed after adjustments.
Usually flyers like wdr on for to overcome the problem you first
highlighted.
I think some cameras it is set to off as standard .
There is a chance you get used to the issue .
Or try to find a better camera (with user interface / osd ) , some soldering and care over voltage needed.
Hope that helps.
Please note I am no expert !
Edit - or is the vtx and camera all one unit ??