The data that would be needed to answer this question quantitatively and predictively (i.e., not measuring stool for example but predicting stool measurements using other data collected from the GI system) isn’t collected in standard American gastroenterology treatment.
The most interesting information I have found so far has been presented by a company called Silver Fern Brand. They are active on Facebook and have some videos there and on YouTube which I would recommend. After the ones on Facebook I would recommend their one about IBS on YouTube, it’s about 30 minutes long.