oh yes - you are right - the west part of the valley is called Kaskasavagge and the east part Kaskavagge.Thank you. That is the app I have been using to explore routes. It is where I found the name Kaskavagge.
I would say both the northern and southern pass are difficult, but in different ways.
If you can cross a glacier e.g. with rope kit safety in a team, the southern is basically a normal walk and not steep at all.
And if you have crampons and are not afraid of steepness, usually the north is no issue either. I advise against going on the western cliffs in that pass as an alternative; have done it with full backpack when I was twenty-one and reckless. But it is an YDS 3+ climb and a lot of loose rocks which can spell trouble especially if you are on a team.
The middle pass is medium easy, nothing else than rough rock terrain with some boulders.