From what I can remember, the most simple way to explain it is, the Brain Octane gets used immediately as fuel, and the XCT Oil has to go through the liver. Correct me if I am wrong.
I usually use the XCT on food, before bed, salad dressing. I use the Brain Octane with my coffee.
XCT is C8 and C10 MCT, Brain Octane is just C8. There isn't that much research on the difference from what I recall.
And yes both can be used in your coffee.