first off a good place to start is using the List View to navigate the blocks.
If you select any Container that is inside the Grid, then you will see in it sidebar Layout options a % width value.
You can change each container independently, as long as the total width of all containers in a grid equal 100% ( or less ) then they will remain in the one row:
If you exceed 100% width the grid will autogenerate new rows for you.
When you create a grid – it will automatically place the Containers for you:
So no need to add container inside them. Just have to consider when they are first added by the grid the containers are just an empty placeholder, they need some content, padding, colors etc for you to see them 🙂