Is it still best practice to include more than one nav element?

I want to create a fixed nav bar and a submenu of internal page links. should I use 2 nav elements, 1 nav and a div or another solution?

Navs are semantic tags: they identify the purpose or role of whatever is within the tag. If you have two separate areas that represent navigation elements, it is appropriate and acceptable to have two nav elements.

Your use case sounds properly semantic.