Question: Bike pants/trousers (prefer compressive)

Hi. I’m frustrated. Basically, trying to find a decent pair of cycle bottoms/pants (trousers) that fit me. I’m 6’-2” and weigh 170 pounds. Those stats seem to put me into either a “medium” or “small” depending on manufacturer. Ordered another pair online that I’ll need to return/exchange. This time, they are a bit too snug in the calf/ankles and being a “small” seem to pull down at the waist. Yet, around the waist and buttocks, they are almost too baggy! Not sure how to say this: I have a flat butt. So there’s some “extra room” down there creating a void and after a while of riding, this ‘bagginess’ causes a rash. Aside from starting to do extensive glute exercises and eating more to gain girth, figured I’d post/ask for some advice on other brands out there which I may not be aware of for better fit/sizing? In other words, any decent name brands out there known for “flat-butted” people like me? Thanks for any name brand suggestions!