You can print on regular paper with tape, but thermal printers pay for themselves quickly once you're shipping more than a handful of packages a week — no ink costs, faster printing, and labels that survive scanning better.

Direct thermal uses heat-sensitive paper that darkens directly — no ink or ribbon, but it fades in sunlight and heat over time. Thermal transfer uses a ribbon to print onto standard label stock, lasting much longer but costing more per label.

Usually it's an underrated box for the weight it's carrying, or too much empty space letting the box flex under stacking pressure. Check the box's burst/ECT rating against your product weight, and fill empty space properly.

Almost always per-unit, but only if you're actually using the volume within a reasonable time. Buying more mailers than you'll use in 6–12 months just ties up cash and storage space for a marginal per-unit discount.

Yes, and it catches a lot of sellers off guard. Even a small, lightweight box can get billed at a higher dimensional weight if it's oversized relative to what's inside — right-sizing your boxes is one of the easiest ways to cut shipping costs.