It helps to understand what is going on when using a DSLR, so for anyone interested in context, here you go
Recording to SD card internal camera follows one data processing path,
But, on Older Cameras from Nikon (and Canon, and others) which were never designed to function as webcams, have had recent mfg firmware and associated USB drivers and software made available, to enable use of DSLR as a webcam easier
HOWEVER, The challenge is that all but the most recent DSLRs have USB2.0 interfaces, and the cameras were never designed to output a full/high resolution image via USB. so your USB data path is often lower resolution (sometimes MUCH lower). An old Logitech C920 produced a much cleaner image than my upper-end consumer DSLR would via USB.
Again, depends on camera model, but often HDMI is much higher resolution output than USB (especially USB 2.0). If you are using HDMI out on the camera, and a HDMI capture card on OBS PC, then you would NOT use a USB connection. If going the HDMI route, then you should be searching for clean HDMI out {and camera / model) to see what settings you need, and potential gotchas. For example, one camera I looked up (not yours) in order to get clean HDMI out required turning off Auto-Focus... so your mileage may vary (ymmv)
Be aware that getting what is known as a clean video out from a camera has NOTHING to do with OBS. And there are better forums for details on a per camera model (at least for my camera mfg that is the case)
Another option, is if the video feed from camera to computer (be that HDMI or USB) has info around the edges (as one would see in the viewfinder), you could use OBS's to simply crop off that info (meaning lower resolution, effectively, but at least clean assuming focus point indicators don't display - red square in middle of original posters Nikon image )
For our church setting, planning for long-term (which we are now at having resumed in-person service recently), the camera needed to be far enough back in the sanctuary, and the lighting not that bright, that an expensive lens would have been required. It was easier/cheaper to simply get a decent PTZ camera. But I recognize some need to make due with what they have.