Well, X3 is "optimized" for SEO ... in which we mean that all fields are populated appropriately. Although one could write a book on SEO, it can often be narrowed down to what is important.
First of all, since you are specifically asking about the URL. Google (and other search engines) are smart enough to figure out what you mean in the URL, regardless of your approach. If you have multiple words, your options would be:
some%20url%20be%20here (spaces)
some_url_be_here (underscores)
some-url-be-here (hyphens)
Why go with spaces? It looks ugly, no professional website uses it, and no search engine would give you any benefit. Underscores? Not a bad option, but it seems very programmatic. My favorite is hyphens, because the url is still readable, yet it does not try to hide that it is an URL. Users are not supposed to read urls to understand the category of the page.
You should NOT use long url's just to improve SEO. Url's should be for humans, and Google have already stated this. Too long url's may be considered as word-spam. Url's have some weight in SEO, but not too much.
Beyond doubt the MOST important factor for each page SEO, is the page
TITLE. It should contain up to 60 characters, human-readable, and it's appropriate if some of the same words are repeated in the page content also.
It's really not much more complicated. Other SEO factors would be external, pages linking to your website, website repertoire etc.