Not sure what you're saying here. You'd set up media queries to use grids to maximum effect for large displays, and single-column/collapsing/flexbox-based schem

Not sure what you're saying here. You'd set up media queries to use grids to maximum effect for large displays, and single-column/collapsing/flexbox-based schemes for small displays. These strategies are not mutually exclusive. Note that grids — in the Swiss design school sense — are about visual harmony, not just about placing things next to each other horizontally.