I did a random check in the net for people with similar OC/voltage of 9700k with top air cooler. It seems your temp is not far different from theirs. Idle temp seems just a little high. But then, there are many factors affecting this:- cooler fan speed at idle, ambient temp...etc
The best way to eliminate the 'case factor' from the equation is:- remove the side panel (and maybe also use a good size desk fan to blow fresh air gently onto the case) and redo the test. So, 'hot air not being exhausted from the case fast enough', 'hot air being recirculated inside the case', 'cool ambient air not entering the case fast enough' issues are all eliminated.