@Lorec do you downclock it or even try lowering the volts it uses at all? I get the idea that these Ryzen's seem to like pushing more volts than they need to, just wondered if you'd tried tweaking that at all?? (I'm very sure that you would have....)
As for the cooling side of things, as I'm very sure you know the ambient temp is going to be the key.. If your going to be hitting 30+ without doing much and your at 82C now (what roughly is the ambient temp now??) I can understand the need for adding another rad or two but it will only take it down to at best your ambient temps...
Daft question and it might not be possible but, have you tried the same setup, outside of the case, just on the side?? Maybe it might be worth a test to see if the case you have is very restrictive with the air flow which is possibly why it's so warm as is??