How does this top fit compared with US sizes?

It uses Asian sizing, which runs one to two sizes smaller than US and European sizes. If you are between sizes, take the larger one. Measure your bust and compare it with the size chart rather than ordering your usual size.

What bra works with an off-the-shoulder top?

You need a strapless or convertible bra, since the neckline leaves one shoulder bare. A bandeau works too. The asymmetrical cut means the strap line is uneven, so check the fit in a mirror before wearing it out.

Is it warm enough to wear alone?

No. It is sleeveless and made of polyester, so it suits spring and summer or indoor wear. For cooler days, layer it under a blazer or cardigan.

Can it be machine washed?

Polyester generally tolerates a cold, gentle machine wash, but the quilting and patchwork seams are the fragile part. Wash it inside a mesh bag or by hand, and skip the dryer to protect the shape.

Is it a top or a jacket?

It is a sleeveless pullover top, not outerwear. Despite being listed among blazers, it has no sleeves, no front opening and no lining, so treat it as a layering piece.