Page format box comes up as default - not page specific. So I can not format individual sheets separatly
You need to use the Styles & Formatting dialog (F11). Derive named PageStyles from the existing ones (context menu ‘New’) as needed. You tghe can assign such a style to the active sheet with a doubleclick in the stylist.
Going Format > Page... > Organiser you also can create page styles, but not assign one by name. (That’s bad, imo.)