The ratios are a side effect not the goal — carbs are a limit, protein is target based on weight & activity level, and fat fills in the rest depending on weight loss goals and satiety needs. This can end up in ratios that look like the various % recommendations you may see.
re: the effects I mentioned, those are some of the possible benefits from extended fasting periods, and I bring them up because a lot of people who elect to do coffee & fat-based extras as their first meal are practicing a version of intermittent fasting. But if you’re just looking at daily intake period, then nevermind 
In that case, for your actual question, I’ve added protein powder to coffee BUT don’t do it when it’s hot!
It will clump and not mix at all.