A simple Wordpress Plugin lets you globally adjust every Wordpress Gutenberg Spacer Block to be a different size on mobile.
The latest stable release for this plugin is available via WordPress
Breakpoint configures the screen width in pixels when the spacers change size. This is the "max-width" for the mobile setting. Any screen size above will use the regular size of the spacer as defined in the block editor.
Ratio defines the amount of change. For example, 0.5 will halve the size, 2 will double it.