I’d like to just add a nav bar centered at the top of the page with no banners, or divider Iines or anything. And mobile responsive with a mobile menu that expands from a button.
Checkout some of Themeflood themes. They’re on sale right now until the end of the year, they all have free demo versions so you can download and try before you buy. There’s even some very nice totally free ones (you should donate if you like them).
Maybe torrent or volcano would be close to what you would like.
I love Will Woodgate’s work, so I did look through all of them but they all have banners or dividing lines or something or other. He just created a theme that would be perfect called “Simplicity” but the mobile menu doesn’t work for me, it opens an iOS spinning 3D wheel which takes way too much fuss and clicking.
I second @teefers recommendation for Themeflood.
Just start with the Blank Theme, perhaps you missed it,
and find a menu stack you like, such as MyMenu and you already have the basic Stacks and that should allow you to do it …