In light of this, Traya is an interesting force user to consider. She neither seems 'beserker rage' or 'focused anger' - she always seemed very calm, almost serene. And yet she was a powerful practitioner of the darkside, but then again she was never really Sith. I'd say Traya is a good example of a darksider who completely mastered and honed her emotions to the point that she no longer needed to incite fear and anger to draw on the darkside...
Theres 2 types of anger i've usually observed. The classic "Berserker rage", and "Focused Anger".
Berserker rage involves in one person lashing out and gaining the tunnel effect, only focused on doing as much damage to the enemy as quickly as possible.
Then there is Focused anger, that makes you sharp and alert, due to the increased flow of adrenaline. When trained properly, focused anger can be very dangerous and very effective.
Thats why it takes more than 1 jedi to usually to kill a sith lord, this is due to their strength and power. But in the end, jedi win because of the berserker rage effect taking over said sith lord. Malgus on the other hand, is quite unique. He seems more effective and powerful when angry, therefore Id say he falls into the Focused Anger category.
In Star wars lore, ive observed that the failed sith lords and acolytes are the ones that have the typical berserker rage mindset or are plain 'weak'.