The main editor widths are set in Settings >> Kadence Blocks. For the best results, set the max-widths to match those of your theme:

Editor Max Widths Kadence Blocks

On a page or post, set the max-width of your editor to better reflect what you will see on the front end of your site. To do so, click the box in the top right of your block setting area and select your desired setting.

 

Kadence Blocks Editor Width