I haven’t seen this mentioned anywhere so thought I would share.
If you want things like videos and other embeds to resize automatically, you need to enable responsive embeds: https://developer.wordpress.org/block-editor/developers/themes/theme-support/
The code specifically for this is:
add_theme_support( 'responsive-embeds' );
It needs to go in your functions (or in the case of Pinegrow custom.php) file.