know if .lib is static or import

Look in its accompanying header files ,if the function are 'decorated' with __declspec(dllimport) that it's an import library. Or look for an accompanying .def file ,that also tells you that it's an import library.

Use the lib command. If it's static, lib will show you a pile of .obj files inside. Not so if it's am implib.

lib /list foo.lib

will do it.

Also see:

https://docs.microsoft.com/en-us/cpp/build/reference/managing-a-library