Most of these workflows go wrong when the steps are done in the wrong order. Cropping after compressing throws away the savings, and compressing twice loses quality twice. Watermarking before cropping can cut your own watermark off the edge of the frame.
The general rule is to make every geometric change first: crop, rotate, resize. Then change the encoding, which means compressing or converting. Add anything that should sit on top of the finished picture, such as a watermark, last.
Because the browser tools run on your own machine, you can redo any step as many times as you like without spending a credit. Only the four Cloud AI tools, background removal, object erasing, photo enhancement and vocal separation, are metered, and none of the workflows on these pages depend on them to work.