Divi Builder has three types of Sections:
Divi already has a Fullwidth section however the modules that can be used inside the Fullwidth sections are limited. Additionally, you can't have multiple column layouts with Fullwidth sections.
If you want a full-width type of section but multiple columns and layouts then this tutorial will help to make any Standard Section show like a full-width section.
Create a standard Section with a normal Row and the column layouts you want.
Add some modules to the columns.
Here's a sample Standard section with 3 columns layout:
Go to that Row settings > Design > Sizing, look for Width and Max-width and assign them both with 100%
Save the Row settings, then you will have a Fullwidth section:
You can narrow down the spacings of that Section and Row.
Go to that Section settings > Design > Spacing and set the padding-top and bottom to 0px.
Next, go to the Row settings > Design > Spacing and set the padding-top and bottom to 0px
You should now have a Fullwidth section layout for the standard section, as seen in the GIF below: