There are two areas to custom options for Careers page and Single post page are Theme option and Custom setting for Careers which located in Theme option ==> Child Options such as Header, Footer, Layout, Page Title, Color, Typography
Any option is set to Default which is the current style of your Theme Option. So, if you want same settings on all pages, then you don't need to select anything. If you want a different option for Single post page or Careers page, then you can choose any other option here as your wish.
You can view the area (1) in bellow image:
If you want a different settings for a page, then you can setup options in Custom setting for Careers and apply it to that specific pages: Single Product and Shop
This is options in Page setting