When add new or edit page. You can change its page title option at the top.
Customise Page Title Typography
You can customise Content Builder header typography, font size etc. Go to Appearance > Customize > Header > Page Title
Customise Page Tagline
You can also add short description about page you are working on. On edit page, look at Page Tagline option.
Header With Background Image
When you create a page or post. You can upload background image to header area. Look at featured image at the bottom right of edit page/post and upload image you want to display as header background image.
Customise Header With Background Image
You can customise page title background image height and other options via Appearance > Customize > Header > Background.