I am using Range and Carbyte together without issue, both do what they are supposed to do and don't interfere with eachother. Once I hit 40mph i am 100% V8 for the rest of my drive. As mentioned above, i also sometimes unplug the Carbyte since it right at my knee on longer trips to get 1-2mpg better.
What someone really needs to make, is to fully disable DFM below 40mph and have it fully engage as normal after 40mph. You don't notice it at highway speed, the jerky crappy driving conditions happen in traffic and city driving at slower speeds as cylinders are popping on and off along with varying throttle input and lots of gear changes. Absolute nightmare of confusion from all of these components trying to work together at slower speeds.