I'm on the remover.work team. A cutout can look clean against one background and still show a halo or a missing detail against another. Here's a quick review step for image background removal.
Remove the background from an image you own, then inspect the preview on both a light and a dark background. Look closely at hair, soft edges, and small gaps around the subject. Check the whole silhouette as well as the close-up: a tidy outer edge is not enough if an important detail has disappeared.