Realistically, while most canister products have their own by the book media setup, media in a filter is customizable.
A general canister setup in order of water flow is: A first stage with one or more relatively course mechanical media, the Eheim filters I have use tube-like rings first, then a course (blue) sponge. (I also have a Hydor canister I'm liking a lot) Next is biological media. Next final filtration with some combination of finer media for water polishing and chemical media (like carbon, carbon infused or other chemical sponge, etc.). A lot of people debate the value of carbon, either way chemical media can be considered optional, it has it's place but it's normally not essential to run full time in a filter. Something like carbon or Purigen, if you do chemical media, can come before final fine media.
Basically, what this does is: 1) filter out large particles first as an efficiency step and to reduce clogging of bio media 2) allow bio media to remove ammonia and nitrite (next insert chemical filtering if you're doing that) 3) final filtering of remaining fine parricides to achieve water clarity. You shouldn't change this basic order, but you can vary which products you use or the proportion of media for each step. I tend to use a bit higher proportion of clarifying media, which for me is simply poly fluff. After a week or two, new poly fluff also becomes bio media. You could conceivably run a filter with all poly fluff-- I've done it on occasion with smaller power filters (hang on the tank filters) for fry tanks. It works.
Plastic bio balls are old technology, really, once popular with people running trickle filters or sump filters, the theory is they create turbulence and add oxygen. But they're not especially efficient in terms of surface area for bacteria. Good bio media has pores that add 'internal' surface area. As a result, rinse or touch a plastic ball and you're wiping bacteria off the smooth, relatively hard surface. Allow exposure to air and bacteria start drying out almost immediately. Bacteria adhere better to rough, porous bio media, plus there are the pores you can't reach. Allow exposure to air and porous media dries out much more slowly, even some partial drying doesn't reach bacteria hidden in the pores.
Ceramic rings for bio is okay, somewhat less efficient use of filter volume than some of the other bio media types out there.
Haven't covered everything, just some basics, hope it helps.
