Re tracing images & then drawing your own adaptations: you import in your graphics program and then use layers above your scan/import file.
If you're really into manga, you might like to check out
Clip Studio Paint which has a great drawing & brush engine and is geared to that sort of thing. Actually, I prefer CSP to Photoshop for raster illustration (non-manga).
FWIW, Ray
Frenden reviews all sort of tablet gear and several years ago I bought a
mid-size Huion 610 for less than $70 based on Frenden's recommendations. It works great, has pretty decent pressure sensitivity, and I like the size much better than the small 4x6 Wacom tablet I had before because the 610 maps perfectly to my iMac screen.
After using a tablet, I can't imagine using a mouse to retouch photos anymore. And all it takes is a couple hours of drawing effort on your part, for a couple days straight, and you'll get used to it very quickly. The surface being slicker than paper doesn't bother me now. Initially I taped a sheet of smooth vellum over the tablet but it wore down the stylus nibs quickly & frankly, annoyed me more than the slick surface.
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Re deleting the original layer, you can do that, or you can simply toggle the layer to hide it. The layer icon that looks like an eye.