If just pasting it’s more arguable, but still likely permitted. If the copywriten characters are the central focus it’s more likely to be infringement.

Adding tracing makes it more transformative, and less dubious. Because of that and the “create a more homogenized image” part it’s closer to a new character inspired by the fusion of others. You’re not using anyone else’s assets, you’re transforming them via cutout, and transforming and adding your own creative work by blending them.