I found the best settings to start off with in Muse are as follows:
The max page width of 1440 pixels is a nice starting point for desktop sites.
Fluid width allows the columns to "stack" on smaller devices. I found the best way to set breakpoints for all sorts of devices is to follow Bootstrap's grid system, http://getbootstrap.com/css/#grid-options
|Extra small devices Phones (<768px)
||Small devices Tablets (≥768px)
||Medium devices Desktops (≥992px)
||Large devices Desktops (≥1200px)
||Horizontal at all times
||Collapsed to start, horizontal above breakpoints
Notice the Container widths! That's where you should set your breakpoints in Muse if you want it to behave like Bootstrap.