Here's the thing: shopping online as a plus-size woman is awful. Most brands don't include sizes and trying to find clothes that are stylish but affordable is very difficult. I think it's unethical to shop at Shein, but if you're a size 4X girl who's just trying to find something modern and within your budget, and Shein Curve has it, go ahead. The quality of the clothes is also terrible, which means that all the clothes purchased at this store will be landfilled within months or years at most.
On the other hand, if you see a fabric h&m or zara and would like to check if a similar fabric exists in Shein, ASOS, Zalando or other stores, you can use Visual Fashion Finder.