A white rectangle remains
Lower the removal strength, check a dark preview, and export PNG rather than JPG. JPG replaces transparency with a solid fill.
Thin strokes look faint
Use a sharper source, move the setting toward preservation, and use Restore only where the original proves the stroke exists.
The signature has invisible margins
Keep automatic trimming on and crop the source roughly around one mark before processing.
Blue ink or notebook lines remain
Use Original or Blue for the ink color, crop lines that touch the writing, and preview on both light and dark backgrounds.