Thanks for the heads up on PinballY. I've been playing with it for the past few days and it's certainly a nice front end.. snappy, open source, and supports batch recording!
It'll be interesting to if PinballY's 'beta' development bridges the various gaps with PinballX, for example..
- Retrieve media automatically instead of relying on a 'let me google that for you' solution.
- Fill in game details (manufacturer, year, etc) from a pre-defined list instead of having to type them manually
- Auto acknowledge dialog option when starting terminals, e.g. missing backglass, authorised to use this rom, etc.
- Hide pinMame dialog
- Fix unicode (e.g. "copyright") and special characters (e.g. '/') handling
- Properly support desktop mode (see below)
- Stability fixes, e.g. crashes 2-3 times when batch capturing video for ~30 tables
- Don't record the "capturing video" dialog in the video when the 'show backglass' option is enabled
- etc
Regarding PinballY's video recording, it's interesting to note it has similar 'issues' to PBXRecorder (prior to my earlier changes)..
- Creates videos using a pixel encoding that isn't supported by 4k PinballX 'planar 4:4:4 YUV'. That said, you could argue the real issue is PinballX should support this format perhaps.
- Doesn't support 'desktop' mode, i.e. doesn't record the videos in the "Tabletop Video Desktop" folder
- Also something unique to PinballY is it rotates the recorded video by 270 degrees even when looking at the table in portrait mode (i.e. desktop mode). You don't really notice this is you're using PinballY to play the video as it 'compensates' for this.
On the plus side though, PinballY's 2 pass video recording is *much* smoother than PinballX and PBXRecorder. That said, I suspect PBXRecorder could be improved easily enough by tweaking the ffmpeg parameters to use the same setup 
ffmpeg.exe" -y -loglevel warning -thread_queue_size 32 -f gdigrab -framerate 30 -video_size 3840x2160 -i desktop -f dshow -i audio="Stereo Mix (Realtek High Definition Audio)" -t 30 -probesize 30M -rtbufsize 2000M -c:v libx264 -c:a aac -b:a 128k -threads 8 -qp 0 -preset ultrafast "video.tmp.mkv"
Anyhow, in short..
- If you use PinballY as your front end then PinballY's recorder is the way to go.
- If you use PinballX (perhaps for reasons above and others?), then you'll probably want to stick with PBXRecorder.. perhaps with some of my earlier tweaks 