On Apache and LiteSpeed, Softminal Cache writes the browser cache and compression rules to your .htaccess file when you save. They sit in a block marked “Softminal Cache”, and are removed when you deactivate the plugin.
If .htaccess cannot be written, the card shows the rules to copy instead. Nothing breaks.
The wp-config.php line
WordPress only loads a page cache early when WP_CACHE is on. Softminal Cache adds this line near the top of wp-config.php:
define( 'WP_CACHE', true ); // Added by Softminal Cache
It removes exactly that line when you deactivate the plugin. If the file cannot be written, pages are still cached from inside WordPress, a little slower, and the plugin screen shows the line so you can add it yourself.