I'm not very familiar with making fonts, so I don't really know what a hardcopy or softcopy is. But if you use Trace Bitmap, and depending on the complexity of the font, there's a good chance it won't come out precisely the same as the original. And I have the impression that the best fonts are incredibly precise.
I would expect a font like is used at the top of the forum pages ("inkscape community") (which is sans serif and rounded corners) should trace fairly faithfully. A serif font or one with a lot of straight lines and sharp corners or a lot of flair or scrolling, or a script font, might not fare as well.
So for that reason, I would say that "manually" tracing would be better.
Edit - Although having said that, if you have a really large original - the larger the original, the better the trace results. If you use an original smaller than an a4 page, the results won't be as good.
For the best file type, you'd have to look into a font-making tutorial, or something. At some point, when you finish drawing the font, the paths need to be converted to a font, and I think there's a fairly specific process for that. But I haven't learned what it is yet.
Oorrr....when you say "scan it up and save it as" do you mean scan it into your computer? If that's what you mean, it probably doesn't matter, as long as it's a format which Inkscape can open or import. But after you trace it, I have no idea what format you need.
But maybe someone who is more familiar with font making can give you better advice.
