when discussing low carb/high carb the only thing mentioned is weight loss. Couldn't there be other benefits when eating low carb (or high carb, for that matter) besides weight?
This is a good question. Low carb diets definitely have some benefits for people who are obese or have certain pathological disorders.
On the other hand high carb diets generally have higher nutrient density and allow the storage of a significant amount of energy(high carb, high calorie diets increase glycogen stores to ~1000g). HC VLF diets also have therapeutic uses in treating heart disease, arthritis, obesity and even diabetes. HC diets also tend to be a lot cheaper and maybe more sustainable overall with the right agriculture choices?
I generally lean towards the opinion that higher carb diets are better overall unless the person has severely deranged glucose metabolism or can't tolerate carbs for whatever reason. I could be wrong though, I would love to hear some more benefits of a VLC diet because I personally don't have a lot of experience with it and haven't done a whole lot of research on the subject.
In regards to your main question there are some studies that allude to a problem mixing carbs/fats in the same meal but I think this is based on the assumption that the fat and carbs enter the bloodstream at the same time. I don't know if that's necessarily true under normal physiological circumstances though.