when we add a widget layout-grid it by default use bootstrap class for columns
an example: col-md-3
and when we need to use mobile version we should add a custom class to work on mobile
like : col-xs-3
if you can add all sizes in class to be a default.
these is definitly a weird thing.
I'm not sure what a good solution would be.
Personally I dont like the interaction of creating, tweaking, managing the layout grids.
I could almost see something being designed as a reference table, but I dont think that would be nice either.
I'd say: don't automatically add col-sm-3 and col-xs-3, as you don't know if the layoutgrid should be displayed the same on all resolutions. But it would be great if the layoutgrid would have the possibility to set all the col-widths without having to write the classes yourself, and also explicitly show the settings.
I'd also suggest to show these in the modeler so a layoutgrid could display something like "3 (12/3)" instead of just "3" when it's col-md-3, col-sm-3 and col-xs-12.