There is no "guide". I guess that some kind of general outline of the effects of removing a given exhaust component would be useful.
My experience, because this is a very objective observation...
On the Fiesta.
If you remove just the resonator, you will get a more "hollow" sound. The noise level will increase more dramatically as you rev the engine. Depending on the internal condition of the muffler baffles you might get a rasping or slight popping sound when you shift.
If you remove just the muffler. You will get much more noise at all rpm. Much more popping and rasping during shifting. None of which i could describe as tuned. It will sound like a car that needs to get a goddamn muffler put on it.
Dual path performance muffler (IE; Borla, Dynomax, Magnaflow etc)
I am discussing these as replacement mufflers on the stock exhaust system. Hanger pins and normal installing labor is required here. That includes welding, cutting and minor fitting. All easily done at a muffler shop.
If you leave the stock resonator and pipe then add a performance type muffler of a close dimension to the original muffler, you will have a slightly more aggressive sound when you accelerate and slightly more pop and rumble during idle. The levels of exhaust note will vary with the brand that is chosen. I love the mellow tone of Borla mufflers at the high end of cost and Dynomax at the more economical end.
Magnaflow is available in a whole system or as just the muffler. They are not bargain bin priced in either case, like Borla or Injen or some of the boutique brands. A buyer can really go off the deep end here! You can literally spend almost the retail value of a average mileage used fiesta on just an exhaust system. And see ZERO performance improvement!
Last but not least. Chambered exhaust. Several configurations are available. Some of these have a fiberglass packing in addition to the engineered internal chambering. Most designs are patented and unique to the particular brand. I love most of the ones i have experienced. They are."un-cheap" but i can't call anything like this "expensive". Chambered exhaust is ordered by length and diameter according to the required or available space. They can provide an almost musical note to an exhaust sound. They are by design, very low restriction. This type of system requires that you have an understanding of the requirements for the best configuration. I had a chambered system on a 1991 Taurus SHO that was just magical. It would pop and burble softly at idle and then simply wail like a banchee at the redline when i was iceracing it at speed. I am biased toward this type of system.