Great review, @user777 !
Gamma curves have been changed indeed, same as several other settings related to Auto Exposure. As I working with mod when have free time (mostly at night), it lacks some testing in daylight conditions, so overblown highlights are quite possible with default settings. But make sure you have latest version of mod installed (released 8 days ago), as it has some adjustments for AE. Also note, that video file recorded with Git2P has YUV format set to TV standard limited range, while actually it is recorded as Full range. Players are mostly ignoring top highlights and darkest shadows and clip it. It should be overriden manually in post, or special effect could be used with mod - Black&White, which transforms YUV from Full Range into Limited Range. In latest version of mod, effect Sepia have been changed in the same way but with increased saturation (crossover between B&W and Colorful). So, I would suggest testing it (with contrast Normal) to overcome highlight clipping and make colors stronger.
As I use my camera mostly indoors, I was trying to adjust it for such low-light conditions - original contrast was too high, image too dark and blurred due to high noise reduction settings, so lot of settings have been tweaked for it. Current settings are still not optimal, and I'm keep experimenting with it. Although, sensor used in Git2P is not the best one for such low light shooting, so now I have switched to Git3 and Ezviz S2 action cameras, which have the same chip inside and quite close firmwares, so it is relatively easy to reuse some findings from Git2P with them, and vice versa, but better sensors for low light conditions.
Sharpening in stock firmware works in following way - edges are detected in image, and one side of it is drawn with darker color, and external one with white. Strength of it could be adjusted with menu options. As for me, it looks too oversharped and unnatural, especially when faces or grass are shot, so I have changed it such way that Low option turns off sharpening completely (as for me, it has kind of analog/film soft look); Normal option disables external white edge, and High works like something between Normal and Low in stock. Another downside of stock sharpening is noise/garbage it introduces: any pixel which has some difference in brightness compared to neighbors is treated as valid object for sharpening, so it becomes darker and white contour is drawn around it. As result, stock firmware has to have high NR settings to blur everything first and then draw dark and white borders around these blurred areas. The higher resolution of image (still/video) and high ISO make it very noticeable. For this reason, I would suggest using sharpness Low, in case ISO is higher than 100-200 for stills in mod, and Normal/Low for video in low light.
As I have mentioned earlier, rolling shutter issue is inevitable with this camera for high resolution video modes, and should be approximately on par with stock for >= 1440p and 1080p60 (and 1080p50 in mod), with exception to 1080p30, which should have same rolling shutter as 1440p, but better details compared to stock one. Also 1080p60 should have same rolling shutter as 1080p30/60 in stock, while still better details compared to them. 1296p30 is upscaled 1080p60 in stock, while it is downscaled 1440p30 in mod (same as 1080p30). 1440p and 2160p (1620p in mod) should be more or less similar (but with lower NR, less sharpening and higher bitrate in mod)
Gamma curves have been changed indeed, same as several other settings related to Auto Exposure. As I working with mod when have free time (mostly at night), it lacks some testing in daylight conditions, so overblown highlights are quite possible with default settings. But make sure you have latest version of mod installed (released 8 days ago), as it has some adjustments for AE. Also note, that video file recorded with Git2P has YUV format set to TV standard limited range, while actually it is recorded as Full range. Players are mostly ignoring top highlights and darkest shadows and clip it. It should be overriden manually in post, or special effect could be used with mod - Black&White, which transforms YUV from Full Range into Limited Range. In latest version of mod, effect Sepia have been changed in the same way but with increased saturation (crossover between B&W and Colorful). So, I would suggest testing it (with contrast Normal) to overcome highlight clipping and make colors stronger.
As I use my camera mostly indoors, I was trying to adjust it for such low-light conditions - original contrast was too high, image too dark and blurred due to high noise reduction settings, so lot of settings have been tweaked for it. Current settings are still not optimal, and I'm keep experimenting with it. Although, sensor used in Git2P is not the best one for such low light shooting, so now I have switched to Git3 and Ezviz S2 action cameras, which have the same chip inside and quite close firmwares, so it is relatively easy to reuse some findings from Git2P with them, and vice versa, but better sensors for low light conditions.
Sharpening in stock firmware works in following way - edges are detected in image, and one side of it is drawn with darker color, and external one with white. Strength of it could be adjusted with menu options. As for me, it looks too oversharped and unnatural, especially when faces or grass are shot, so I have changed it such way that Low option turns off sharpening completely (as for me, it has kind of analog/film soft look); Normal option disables external white edge, and High works like something between Normal and Low in stock. Another downside of stock sharpening is noise/garbage it introduces: any pixel which has some difference in brightness compared to neighbors is treated as valid object for sharpening, so it becomes darker and white contour is drawn around it. As result, stock firmware has to have high NR settings to blur everything first and then draw dark and white borders around these blurred areas. The higher resolution of image (still/video) and high ISO make it very noticeable. For this reason, I would suggest using sharpness Low, in case ISO is higher than 100-200 for stills in mod, and Normal/Low for video in low light.
As I have mentioned earlier, rolling shutter issue is inevitable with this camera for high resolution video modes, and should be approximately on par with stock for >= 1440p and 1080p60 (and 1080p50 in mod), with exception to 1080p30, which should have same rolling shutter as 1440p, but better details compared to stock one. Also 1080p60 should have same rolling shutter as 1080p30/60 in stock, while still better details compared to them. 1296p30 is upscaled 1080p60 in stock, while it is downscaled 1440p30 in mod (same as 1080p30). 1440p and 2160p (1620p in mod) should be more or less similar (but with lower NR, less sharpening and higher bitrate in mod)