Does having a keyword in the domain repeated again in the path of the URL hurt SEO?
No.
Which of the following URL structures would be best...
Best for SEO - either. Best for users - probably the shorter one. "fishing-lure-companies" doesn't really make a whole lot of sense to me? URLs that are better for "users" indirectly benefit SEO.
Would repeating the keyword in the first URL be considered keyword stuffing
No.
Bear in mind that "keywords" in the URL carry very little weight in terms of direct SEO (a factor that, by itself, would directly affect ranking). On page content is the key here.
URLs are primarily for users and can help click through rates. Search engines don't care so much. /?id=123
or /fishing-lure-companies
- it's really the content that the search engines care about.