Start with the effect you enjoy: curved outlines, straighter edges, a subtle rim, or a more visible frame. You do not have to follow a face-shape rule to choose glasses you like.
Save one round and one rectangular model in similar colors. Compare their measurements before judging their appearance; a larger frame can change the impression as much as the shape.
Use virtual try-on as an appearance experiment and check the actual product photographs for model and color detail. The preview is illustrated and cannot establish physical fit.
When you have a favorite shape, compare two models within that collection. Review dimensions, color availability, and the complete lens estimate before making a decision.