Custom or Built In Nav Menu?

Just wondering whether there are any SEO advantages (in terms of mximizing the number of internal links) if I create my own text-based navigation buttons rather than using the built-in nav menu. Maybe the text in the built-in navmenu is viewed by search engines as a link anyway?
Any thoughts would be appreciated

As far as I know, only external links may influence SEO. Am I wrong about that?

Thanks Rovertek
Not a make or break SEO factor for sure, but info such as this ( tells me it’s worth considering.