I have no "Element Spacing" option in my customer for GP Premium.

Correction: I see spacing in the "add-on" section and its activated, however, when I got to my customizer to begin designing, I have no element spacing and can't seem to find out where to set letter spacing for my navigation buttons and so on.

The Spacing options are in their respective element section in Customize > Layout.

More info here: https://docs.generatepress.com/collection/spacing/

Ok, I found that. Is there no way to customize the letter spacing between the nag items in the options given?

Letter spacing for menu items can be changed using some CSS:

.main-navigation a {
    letter-spacing: 1px;
}