Changing the tip (the end pipes sticking out of the muffler) is more cosmetic than anything. You can get different sized silencers the diameter of the hole will determine how restrictive or quiet it is. You can also remove it when you want to, however will you?

The resonator doesn't restrict flow, it's often an increase in pipe diameter in the middle of the exhaust system to reduce certain sound frequencies or drone. While driving you might notice cabin noise resonates and gets louder at some rpm's, this helps match those frequencies to cut them out. Doesn't decrease overall noise or sound.

You could just change out your muffler, second hand will probably be just as good. If your lucky you could do it yourself and just bolt it on. You may need someone to weld it on for you, but you should be able to find a cheap second hand solution.

You could swap in a Varex muffler if you wanted and flick the switch to quiet before you enter the street. Much better than a silencer, I don't see the point in getting a noisey cannon then trying to silence it anyway.