+x"Use Route Level" just means that the leg does not have its own level specified; the general level for the whole journey is assumed (set in Flight Details).
The documentation will tell you more about MSA, but in general you control the planning options responsible for calculating your MSA. It consists of horizontal and vertical proximity to terrain. You may wish to make these corridors quite narrow if you're flying in the mountains, and I would especially advise you to take advantage of our Colour High Terrain feature so you can see exactly where the high terrain is.
Having flown ALPs a lot now, I have found that the Austrian GAFOR track Refernce Alitude is always a good reference for flight planning.
The Ref Altitude is published by AustroControl for planning purposes.
It indicates the highest altitude at which the valley of the route is still at least 1200m wide.
If the Ref Altitude is used, there will always be a difference between the calculated MSA in the Briefing Pack / PLOG and this value.
This is understandable since SkyDemon uses the calculated MSA while the pilot uses the Ref Altitude.
On the other hand, it is annoying when an MSA is always displayed in red in the PLOG.
Would it be possible to link the MSA with the Ref Altitude in the PLOG to avoid the disturbance caused by the red color?
Maybe as a checkbox in leg properties ?