It's, generally, a hard style, emphasizing striking and grappling, along with weapons skills (including firearms)
Systema is generally soft and it does NOT emphasize grapping at all, when you grap someone you lock yourself up with the opponent and you cannot grab them as well as hold onto your gun, knife, or club.
As far as disarming goes, the man is the threat and not the knife, the knife is only an extension of the threat. You might attack the limb holding the weapon or the person but your aim is not to hyperfocus on the weapon and destroy the man.
The "psychic energy" tapes goes into using a person's reflexes against them. Look at it this way, if I were to slowly put my hand near your crotch or face you'd probably make a sudden move away from my hand. I am not touching you yet you still moved, so if one knows enough about those reactions you can exploit them in you opponent.
We don't have preset forms or techniques in Systema, the idea is to let go and allow your body to do what it wants. Many times in class I will attack a student and they will dispatch me in some way and I'll ask them exactly how they did it and they are not sure or will have to think about it.