The size of opened widgets is often much to big in the mobile Layout.
For our Homepage we're embedding WebApps (made with ArcGIS Online WebApp Builder ... so we have no possibility to configure anything by coding) in iframes ans switch the layout to mobile to save space.
But a lot of the widgets which wouldn't need so much space use it regardless of their content. For example the basemap change:
There is too much white space and the widget covers half the map.