The sizing gap is real and roughly predictable
Chinese domestic sizing runs approximately one to two sizes smaller than the equivalent US or EU label. A Chinese "L" is closer to a US "S" or "M" depending on the garment. This is not deception; it is a different domestic standard that many brands have never fully converted when they open an overseas storefront.
The practical defence is to ignore the letter entirely. Look for a measurement chart in centimetres giving chest, waist, hip and length separately, and compare it against a garment you already own that fits you the way you want. Measuring your body and comparing it to a body chart is less reliable than measuring a garment, because garment measurements include ease.
Colour and fabric are the harder risks
Distance makes two things expensive: discovering that a colour reads differently from the photographs, and discovering that a fabric composition is poorer than implied. Polyester-heavy blends at premium prices are the most common complaint in this category.
Composition and weight are the specs worth checking. A listing that states fibre percentages and grams per square metre is a listing from a brand that knows its product. One that offers only adjectives is not.
Returns: do the arithmetic first
This is where most of the money is lost, and it is not about the window length.
An equal-size return to a domestic warehouse is cheap. A return shipped back to China for a $40 garment typically costs more than the garment is worth, so the 30-day returns policy is, in practice, a 0-day returns policy — you will simply keep it.
So the question to ask is not "does it accept returns" but "where do returns go". If the answer is a local address, you are dealing with a real regional operation and can buy with normal confidence. If it is China-only, price the order on the assumption that it is final.
What to order first
Start with a single low-risk item: something where fit tolerance is generous and colour is not critical — a scarf, a bag, a loose overshirt. That tells you how the brand's sizing maps to your own body and how they handle a problem, before you commit to an order where the answer matters.
Sizing standards, textile labelling requirements and consumer return rights differ by country and change over time. Verify against your own jurisdiction and against the brand's current published policy.