Normally you would legend() instead of adding markers to a title()
With regards to the output size, are you referring to "as drawn" or "as printed" ? If you mean "as printed" see the figure PaperSize property. For "as drawn", you can set the figure Units property to pixels or inches or cm as appropriate. As you perhaps asking how to disable the user from resizing the figure?
Subplots do not have figures: they are axes. You can resize an axis by set()'ing its Position properties. Note that each time you call subplot(), if the calculated position of the axes being requested overlaps any other axes, the axes that are overlapped will be deleted.