Hi there!
Thanks for your query.
If you bound the container width in the template settings, then SPPB settings will not override it as SPPB works within the component area. Outside the component area is under template's control.
One thing you can do is, you may left your template as fulwidth and then you can choose from SPPB sections that if you want that specific row as fulwidth or not. But as I can see you are using a really old template here, based on Helix V2, which is not supported anymore. This template doesn't have fullwidth option I think.
CSS customization can be done by playing with negative margin of that section, but maybe it won't be perfect for responsiveness of the website.
https://prnt.sc/rQBwS9oB9sxN
After setting negative margin you can play with the container width of the specific section if needed:
https://prnt.sc/khEzXR5wlHq-
Hope you understand.
Best Regards