The "simpler" methods of just adding calcium, bicarbonate and magnesium and regular water changes are actually quite regimented as regular testing of water quality and parameters and good nutrient export still need to be practised vigorously for sps corals to take root and grow with good colouration.
From my personal experience, the major difference between simpler regimes and those that employ more supplementation is the utilization of probiotics. Bacterial supplementation will reduce nutrient levels by another degree which would enable tank owners to be able to keep more fish and/or more demanding SPS corals such as certain challenging species from Fiji and Tonga waters.
Which method of probiotics one prefers is a matter of personal choice, budget and dedicationas a variety of options exist such as DIY vodka dosing, biopearls, fauna marin's ultralith system (which I use), zeovit, Redsea's Nopox system, etc or even comibantions of 2 or more methods.