The only filter I use is in my Savinellis and I only use this in wet tobaccos and aromatics. I don't like like metal or paper filters much, but I have not found that they change the flavor very much.
What pawpaw said if it makes a difference to you that's all that matters... no particular right or wrong when it comes to that. Piping is all about personal experience and expression Put ya pipe on and let ya soul flow
A stinger is the metal piece that is usually connected to the stem of some older pipes and some new ones at that! Here is an example...
It is said to condense the moisture in the smoke and provide a cooler and drier smoke.... Whether it actually does is still up for debate! Hope this helps!