I am yet another spread sheet freak. I customise it to what I want. I keep track of everything in one Excel book - BG levels, weight, blood pressure, liver & kidney functions, cholesterol & lipids, full blood count results, other blood test results, and when I was keeping one, my food diary. I have graphs for some of these things, and do my own averaging.
I agree that myfitnesspal has a lot of incorrect carb counts and also other nutrient counts. I also used to enter my own bespoke ones rather than risk theirs in the days when I counted to that extent. I don't need to count these days.