Is there any way that provides data from component description without having to resolve the component, and is at the same time quicker than traversing feature tree nodes (.TreeControlItem), which is very slow for large assemblies?
SWDocumentMgr should be able to do that for you.
2017 SOLIDWORKS API Help - GetCustomProperty Method (ISwDMDocument)
By resolving you mean lightweight components? If so, here is a faster way to get the model doc from lightweight component: Get Model Doc from lightweight component using SOLIDWORKS API , it is still loading the model, but doesn't open that in the new window. Otherwise you can follow Simon's suggestion with document manager, here is an example: Read All Custom Properties using SOLIDWORKS Document Manager API
Retrieving data ...