More than any clever combination does. Build from what you already own in one colour family, plan a single wash mid-trip, and check your airline's real limits rather than assuming carry-on works.
Plan one wash and pack for half the trip. That single habit removes more from the bag than any mix-and-match system, and it's the thing packing guides skip in favour of outfit grids.
The striped top doesn't work with the patterned shorts because nobody chose a palette before choosing clothes. One neutral base and two accents, decided first, and the problem disappears.
Four tops by three bottoms is twelve real pairings. Counting a cardigan swap as a separate outfit is how the number reaches thirty — and nobody experiences it as thirty distinct looks.
Cabin allowances vary enormously between carriers and fare types, weight caps as low as seven kilos exist, and gate charges cost far more than adding a bag at booking. Packing perfectly for the wrong limit still fails.