Ah I see what you are getting at now :-)
OK a few options, I'm going to assume your Settings, Video, Base Canvas is set to 1920x1080 if it's not it should be
Easy - Record yourself playing a game, open the video and make it full screen in your chosen player, Use NVidia screen shot tool
Easy (ish) - give your artist the position of your camera by doing the following, Right click your webcam source and choose Transform, Edit Transform the Position and Bounding Box Size should be enough information.
Depends - Right click your scene and choose Fullscreen (Projector Preview) and choose a second display that's 1920x1080 - take a screen shot, Nvidia has a built in screen shot tool I used in this situation
More complicated - Create a new Profile and a new Scene Collection, Set your Base Resolution to 1280x720, set up your scene how you want it. Right click your scene and choose Preview Scaling, Canvas (1280x720) Now your preview is at the exact resolution you defined. Make OBS full screen, use the Windows Snipping tool to copy the Canvas and then scale it to 1920x1080.
There's a reason this is so complicated, the complete scene inside OBS is only rendered to the stream or recording. It's OK if you have multiple monitors as you can use Projector which also shows the full scene but if you only have one display you have to think more imaginatively. Option 2 is how I've created overlays in the past and I'm no artist so if I can use the Transform data your artist can :-)