There really is t a use for max end stops since most slicers require you to define the bed size. and like I said you will not be doing yourself a favor if you only place end stops on x and y. without a z end stop you will drive into the bed on auto home. you can use an end stop that will stop the nozzle or tool from reaching past zero. but in most 3d printers you have either an arbitrary mechanical switch that you will have to adjust the bed to, or you will have an inductive of capacitive probe that will be set to an offset of the nozzle height. with both inductive and capacitive probes you will need to set them and auto home only when you are heated up, otherwise you risk driving the nozzle into the bed. until you understand the inner workings of these options then I would advise you to stick to manual home setting. there are many different models on thingiverse for adding endstops to the mpcnc. it depends on what kind of end stops you go with.