What do Windows Registry Editor "InProcServer32" Keys and "ThreadingModel" Strings do? Newbie explanation please.

I want to add custom shell folders to ThisPC. I am using existing Shell Folders like Control Panel Applets or UserFolders as guides. I am not editing existing entries but rather creating new ones and I am reasonably experienced with windows customization through the registry but I am not a coder/programmer.

For InProcServer32 Keys, the main choices for Control Panel Applets and ThisPC Folders seem to be either shell32.dll and windows.storage.dll. What is the difference between the two and how do I choose? There doesn't seem to be any icons associated with windows.storage.dll so InProcServer32 doesn't look like it is points to resources.

For ThreadingModel, seems like the major choices are "apartment" and "both". Again, what is the difference between the two and how do I know what to choose?

Thanks!