I did not touch the server level cache module, just set "storagePath $VH_ROOT/lscache" per virtual host cache module, and it works from my test(/var/www/html/lscache/priv/3/0/5/xxxxxxx).
To set up the handler, you first need to configure the external app. You can follow the instructions here:
https://docs.openlitespeed.org/config/php/externalapp/
Since you are using CyberPanel, this step is usually not necessary. Are you trying to customize the PHP configuration?
To set php_value, env variable may not work; please follow https://docs.openlitespeed.org/config/php/externalapp/#override-the-global-phpini to set the value per virtual host.