@stiebs Hopefully this clarifies some things.
PMV /= PSV. They incidentally both work in a very similar fashion in that they are downstream valves designed to maintain pressure, but they are two separate devices with very different purposes.
PMV is a pressure MAINTAINING valve and is located right after the filters. It is set somewhere around 150bar ish which maintains pressure inside of the filter stack. Regulators like your first stage maintain a certain IP regardless of tank pressure, and a PMV is a backwards regulator that maintains some minimum pressure behind it and once that pressure is reached, it lets gas through. I.e. if the compressor is at 100bar, it will keep running with 0 air coming out of the whips until it hits 150bar, then once it hits 150bar, it will maintain that 150bar behind the PMV even if the tank it is filling is empty. This is the MOST critical part of your filter system and often times the least understood. The PMV is placed AFTER the filter system, but BEFORE and pressure regulating devices and whips. It is usually screwed into the final filter tower and then any fill whips or regulators are screwed into it as shown in the diagram you linked above
PSV is a pressure SAFETY valve and is also called a pressure relief valve/PRV or just overpressure valve/OPV. It is a legal requirement for safety to make sure that pressure above the working pressure of a vessel is bled so it doesn't explode. On a scuba valve it is a burst disc, on first stages it may be built in like Poseidon, be screwed into a LP port like on most argon/CCR O2 bottles, or the system will use a downstream valve like a second stage to bleed excess pressure. These OPV's are typically set a bit above the working pressure of the system. On a compressor that may be 300bar if it is filling HP bottles from Europe or bank systems, 250bar, 200bar if only filling AL80's, etc etc but all it is doing is setting that overpressure valve so the system does not build excess pressure. It is a safety device and is usually used in conjunction with a pressure switch that will turn the pump off before the valve releases.
The changeover device is a fixed pressure regulator, basically a scuba first stage that has an outlet pressure set to 230bar.
In Europe, there are actually different DIN fill ends for both 200 and 300bar. They use short DIN for 200bar which will not screw into a 300bar valve because it only has 5 threads instead of 7 so it won't seat, and their 300bar whips have a nipple on the end that prevents them from seating into a 200bar valve. We do not use these in the US and our DIN whips look exactly like a regulator din connection which is universal. Bauer is a German company and has to comply with CE so they have a changeover device option to allow you to fill both types of tank valves off of the same compressor.
In terms of filling. Your compressor won't really notice or care whether the device is open or not. The PMV will force the compressor to pump at a minimum of 150bar, and once it is above that, it will fill the tanks until you turn it off, or turn the fill valve off and it runs until it hits the cutoff pressure. The PSV on the changeover device is there to protect the whips and tank from high pressure if the regulator itself fails and has high pressure creep, the same phenomenon that our scuba first stages are prone to
Personally? I would get the 300bar setting, use a "normal" DIN whip that will fill either style of tank valve, and just pay attention when filling and/or add either an adjustable pressure cutoff switch so the pump itself cuts off at whatever pressure you want, or add an adjustable regulator so you can control the pressure that the tank fills to.