Custom Layout Section will let you drag and drop sections, so you can design your own checkout page.
Video Guide:-https://www.youtube.com/watch?v=ODMMvu2xQbw

Select a section from the left and drop in your desired column. You can also select different columns. See screenshot:-

For every section, you are dragging from left it has some inbuild settings. Open any section for example:- “Billing Details”.

• Hide Label:- You can select whether you want to show header for a particular section or not.
• Background Color:- You can change the Background Color for a section.
• Padding:- You can assign some padding in case.
• Click “Save changes”.

Custom HTML section:- Custom Html section is a new feature that will let you add your shortcode or custom messages on the checkout page. see screenshot:-