When normal flow gives you the layout you want use it. If most of a section you’re laying out follows normal flow let it. Wrap the section you need a different layout for in a div and use Flexbox or grid just on that section. There’s no need to fight with Flexbox or grid to get back to a normal flow. Flexbox and grid can be used surgically to change layout where you want it changed. And they can be used in combination.
Getting Braaains Should Be Fun