The distro choice isn’t that difficult, as if you have experience with Linux you know what you need, and if you don’t, just choose any beginner-friendly distro (probably Ubuntu flavors and Mint).

I prefer LibreOffice’s ugliness to Microsoft’s strange menus. Anyway they’re also available in LibreOffice, in the view menu.

For the rest of the interface you could look into GTK themes, I think LO’s looks depend a lot of the theme you use. The interface is pretty customizable, I think.