So the "fusion" is really just a mixture. It is not required to decarb to get a good mixture.
If you are going to spread your butter on a slice of bread, then you will need to decarb anything you add to the butter if it is not already. If you are going to bake with it, probably not.
Butter or coconut is not really important. If you want it to stay liquid, you can use MCT oil. Sunflower oil is high in Lecithin and has been shown to improve uptake of cannabinoids. You can add that separately as well.
Depending on how the concentrate was made, it may or may not be decarbed already. What is the source? If you got it at a dispensary, post a pic of the label and I can tell you.