Design for the smaller decision surface first: essential information, comfortable targets, predictable controls and fast feedback. Then enhance the layout when more room is available.
Test sticky actions, filters, media galleries, variants, keyboards and error states on real devices. These interactions expose issues that static screen reviews miss.
Keep content honest about available space. A shorter, clearer hierarchy usually performs better than hiding a desktop volume of copy inside accordions.
Choose one high-value journey, document the current evidence and give the next change an owner, a success signal and a review date.