I am doaseing the BRS 2 part so keeping mag consistent is important. Elevated mag levels will reduce algae and keep the 2 part from binding together allowing it to be more easily consumed by Stoney corals. Most people still run mag from 1300 to 1350 and seldom dose it by hand or automatically unless it is dominated by SPS. When my wife had a strictly softie tank I always maintained it at 1500. In Europe it is not uncommon to read of reefers maintaing 1700 ppm levels due to the balling method that is very popular there. I know of many reefers who also maintain it that high due to the consumption rate of species such as acro's and cap. You are correct the BRS mag is much lighter on the wallet but the tech M is great for nuisance algae such as turf algae. I usually recommend a mag level of 1500 for most mixed tanks. It has been my experience that the corals color up better and display much better extension. Switching to just Kalkwasser instead of 2 part would depend mainly on your live stock from my perspective. If you mainly have soft corals then Kalkwasser is an easy way to maintain Alk and calcium levels but you then need to keep an eye on your Ph. If you are running a calcium reactor then Kalkwasser is all you really need. If your not running one 2 part is an easy way to manage both Alk and Calcium . I know people with beautiful SPS tanks that only use kalkwasser but are constantly fight the Ph in their systems. There really is no wrong way just the way that works best for you and your system honestly. Good luck !