nothing is a "must" - as long as you have a working system/plan to replenish the good things and remove the bad. a fuge with cheto is a very easy way to export phosphate and nitrate and culture pods and plankton for food - but there are plenty of other methods. many of the better systems attack the same problems from multiple angles.
here are the some of the basic goals most try to achieve with their filtration systems, and a few of the tools to do so off the top of my head:
1) bulk waste/detritus removal - mechanical filtration, filter socks, sponge filters/pre-filters, vacuuming(water change), settling tanks, etc
2) fine waste and water clarity - protein skimmer, diatom filter(temporary), activated carbon or similar, bacterial dosing or cultivating(carbon dosing).
3) nitrate reduction - macro algae culture and export, bacterial dosing (with skimmer), bio-reactors, chemical additives, water changes, etc
4) phosphate reduction - macro algae culture and export, bacterial dosing (with skimmer), phosban-reactors(or similar, like ferric oxide), chemical additives, water changes, etc
5) oxygen/gas exchange - pumps. water flow and surface agitation. surface skimming.
there is lots of overlap - but i would say if you intend water changes to be one of your primary nutrient exports, you should plan on larger than 10%. it will really depend on the nutrient import and uptake. for small tanks its easy enough just to do 50-80% water changes once or twice a week, but for large tanks it can be a pain to keep nutrients low with water changes alone.
here is a nice calculator to see how water changes add up over time: http://reefcentral.com/index.php/rodi-calc