Full width nav bar vs fixed width

I see a lot of websites where the main content and main menu bar (logo, menu, login/signup) have a fixed max width, even when the user is on a wide monitor (>= 1920px). The logo lines up with the content on the left and the login/signup links with the right. The fixed width might be around 1200px to 1500px.

I see other designs where the content is a fixed width (1200px to 1500px) but the nav bar is fluid and fills the width of the screen (>=1920px), so the logo and login/signup sit away from the content on right and left sides on large screens, like below:

My question is whether this is bad UX?

I am worried that the login/signup links, and to some extent the logo, get lost because they sit out by themselves.