200watts of panels rating is factored on clear skies, perfect alignment, mild temps
etc.. so i would expect maybe 150-175watts output to be more real world output
and then when the panels are fairly close to alignment with the sun and clear skies
average year round output.

i am tbinking you will be doing well to see a 10% gain using mppt with 200watts rated panels going into a 12 volt bank, overall average.

maybe a bit more if you are very careful and lucky

in my opinion on small systems, the money might be better spent on more panels instead of an expensive mppt, unless one is planning on growing the system and going to something like 48volts nominal in the future.