Is there any difference between installing a package and using #include <lib.h> and manually downloading the source of the code you want and using #include "lib.h" other than the location to be searched? assuming both have the same versions
Does the installing a package way install a shared library or is the code statically linked into the program as well?
Linking and header files are unrelated things.
The only difference between <> and "" is searched location.
Linker does not know anything about the header/source files that were used to create the binary module being linked.
Typically you use the <> for things like system header files or STL files because they are not part of your project. You use the "" for your project files. It changes the way the compiler searches for the actual files. The system headers are not going to be within your project folders so it doesn't make sense to include them with the "" notation.