There are LOTS of possibilities.
Personally, I set up PowerPoint slide show (Service Bulletin) as a Windowed Slide show (not full screen) and display/capture that on OBS Studio PC (no in Sanctuary displays)... but worship style, PPTx content, etc all come into play...
For context, I have Scenes for Full Slide (Portrait mode), Partial Slide, and No Slide
In Full Slide, PPTx is about 1/3 (to 40%) of the streamed video width, with rest coming from PTZ camera
In Partial Slide, PPTx is about 1/4 (or a bit less) of the streamed video width,
In No Slide, PPTx is not displayed, and 100% of the streamed video width is the camera
As for you, I wouldn't do any of this over WiFi.
In your case, if laptop Ethernet wired (NOT WiFi), you could run software that creates NDI output and send that to OBS Studio PC. Or you could capture the HDMI output (there are both HDMI to USB adapters, as well as HDMI to Ethernet... depends on your specific setup).
My personal recommendation, presuming preacher ok with it, and volunteers up the the task, and OBS Studio PC properly/adequately configured.
- Let the preacher preach, and someone else runs PPT from OBS Studio PC..
If preacher just can't let go of manual slide advances, there are options for letting PPTx run on OBS Studio PC and that alone be controlled by preacher ... can't be simple presenter/pointer, at least the ones that mimic a mouse at Operating System level as OBS Studio operator will be using mouse, so that would cause an issue. But a remote that only talks to PPT could work... or software on Preacher laptop that sends commands over network to OBS Studio PC PowerPoint (and that should be fine over WiFi, presuming solid/stable, isolated from guest/parishner WiFi, if such exists)
There are command line options. There is WebSocket, etc.
- Do HDMI output of PPTx slide show from OBS Studio PC (on own monitor) and send that to both projectors.
And Yes, presuming Full output Screen of PPTx or Camera, yes you could have a Scene for each and switch back 'n forth as desired
Though consider if you need Full Screen PPTx, or if a Picture-in-Picture display might work better, with smaller PPTX window overlaid on top of camera view??