Sorry if this has been asked before, but I just saw that the product page for the GNS 530/430 states that it is compatible with MSFS? Can anybody confirm that it really works just like in P3D, with a 2d pop-up window that can be dragged to another monitor? I'm asking because I never read any news about it being compatible and after MSFS was released Mindstar was skeptical if the SDK even allowed for their product to be ported over to MSFS. 

I can confirm that it does NOT work with MSFS 2020.  The acronym MSFS was around before the current product release by Asobo, and that web page was made before MSFS 2020 existed.  Right below the line you're using as reference to compatibility is a list of requirements.  The first one tells you what sims are supported by indicating that at least one of them is required to be installed to use the 430/530.

Requires either Microsoft Flight Simulator 2004, FSX, FSX: Steam, ESP, or Lockheed-Martin Prepar3D (V3 and lower).

Thank you for the confirmation, sad to hear though.