I’ve made the change to the new responsive engine and it seems quite intuitive, except for one part where I am completely stuck. At the bottom of my page I have a 4 column repeating group to show recommended listings.
If you’ve enabled the Set fixed number of columns setting for the RG, then that’s exactly what you’ll get. The number of columns will remain the same regardless of page width.
You don’t explicitly state it, but it sounds like you want the number of columns to decrease and for the cells to stack on smaller devices - i.e. a more responsive behavior. To do that, you must DISable fixed number of columns and proceed as @rpetribu suggests.
But with 5 data entries to test, it shows all 5 while I just want it to show 4. This means that on desktop these columns are scaled down a bit too much and on mobile you get a vertically scrolling RG.