We would like to recommend Setting up page width.

Hi

Thanks for contacting us. Could you please explain it more?

-Regards.

Hi Chatapol,

I also don't fully understand what is your goal.

You want to reduce template width from full width with container to Box layout ?
If yes, check Template Options > Basic > Body > Boxed Layout : YES

then choose bg color for the website, maybe white?

For other width changes you have to use your CSS knowledge, no options/switchers for that.

Page content (from SP PB) that is displayed in component area uses class .sppb-row-container

and on large resolution this default value is used

  @media (min-width: 1380px) {
.sppb-row-container {max-width: 1320px; }
    }

As you see very basic CSS. We cannot teach CSS here, so we can give only tips.

Yes, you can override it using Custom CSS.