@Rocky-Hill Okay, if in Rpi3 the same configuration works, I suppose the problem is in the RPI4 detection of EDID: your iMac G3 DV monitor is not being able to communicate correctly with RPi4.
- Have you tried with both RPi4's HDMI ports?
- Have you tried with another HDMI adapter?
Analyzing the CHANGELOG of the next version of Recalbox (https://gitlab.com/recalbox/recalbox/blob/master/CHANGELOG.md), it is noticed that there are some changes related to Rpi4, such as:
- Fix detection of 4k screen (I know your monitor is not 4k, but it is also about screen detection)
- B*mp RPI4 kernel (may be related)
I believe that in the next version this error can be solved, if you are patient, wait for the next version and test.
If you are impatient, test the following:
- Use the default video setting, leave config.txt unchanged (commented out as you did)
- Turn on the monitor first, start Recalbox
- If the resolution is distorted even after starting the Monitor first, disconnect and reconnect the HDMI cable
- Regardless of the resolution, if possible, try to start an NES game