The cooling system really doesn't care what degree thermostat it has, it will keep it cool (or not) regardless down to that temperature.
Now if the cooling system is undersized or having other issues that is keeping it from being able to cool the engine properly all that a lower temp thermostat is going to help with is delaying the engine overheating by a little longer.
For example, say your engine runs at 210*F because the cooling system can't keep it any cooler than that. Let's say it takes 1 minute of run time for the engine to reach 210*F with the 195* thermostat. Now if you put a 160*F thermostat in place, the engine is still going to reach 210*F because the cooling system can't keep up. However since the thermostat opens sooner it lets the coolant get a head start on cooling (so to speak) which means you now go from 1 minute of warm up time to say 5 minutes before you hit 210*F.
You may have already known this and it doesn't really have anything to do with your original post but is something to think about. A lot of people think if the engine is overheating that they should install a colder thermostat but that is only a bandaid for a problem somewhere else in the system.