Would be great if you could choose a template for these different from the notebook settings, so you could add a math equation to your text page without needing to change the template of the whole page to squares.

But only an option. Either None, date or date and time. You could also add an option for adding page numbers on the page. It should be an element like a normal text element, so you can move it around or change the color on a single page if you want to (maybe because one page is a picture with a darker background, so you want white date instead of a black date).

I think it would make more sense to leave the paper in the color that it is and also not switching ink colors. That way, your note would look the same in all scenarios. Colors like dark green aren't really visible on black. I think it's enough to make the interface and menu (and the margins next to the page) darker, but not the page itself. If you want black paper also, you can already chosse a "dark" color option for the paper in your note settings.