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) |
| Grid behavior |
Horizontal at all times |
Collapsed to start, horizontal above breakpoints |
| Container width |
None (auto) |
750px |
970px |
1170px |
Notice the Container widths! That's where you should set your breakpoints in Muse if you want it to behave like Bootstrap.