Bimmercode messes with every module in the system
Auto start/stop is in the Body controller though, yes.
I definitely think it's best to drive the car as-delivered for a while, if only to get a feel for what you might want to tweak. And, there are so many zillion ways to tweak it, you'll want to think through what you want to do. I ended up only doing a few things. Have a spreadsheet here somewhere, if you're interested.
BTW the "ECU" is called the DME in these cars.