Kadence - Content & sidebar widths
Kadence allows you to fine-tune every aspect of your site, and that includes the content width and sidebar width!
Overall Content Width
Go to Appearance > Customize > General > Layout. Under Content Max Width, change the px value to your desired content width. For most sites, somewhere between 1100px and 1400px looks best.
Sidebar Width
Go to Appearance > Customize > General > Sidebar. Under Sidebar Width, change the % value to your desired sidebar width. If you prefer to set a fixed width (not a percentage), click on the % icon and select px.
Content and Sidebar Width when using the sidebar shortcode
If you're using the Blog Layouts alongside the sidebar shortcode, your content and sidebar width will be determined in the block settings. Go to Pages > All Pages and click Edit on the page you'd like to edit.