I want to do a full backup of my Mac to an external disk AS FAST AS POSSIBLE. Does that mean I should use something other than Time Machine or set some settings?
It depends on what your full usage scenario is. For a one-off full image Time Machine is not very well suited, you are better of with using
If you are looking for having a full image of your drive updated regularly, fast and hassle-free, Time Machine is a good way to do that. The initial backup will just take a while longer, the incremental ones will be rather fast.