CWP Pro PHP switching is for use on a per user/domain basis. Example one site might use 5.3 whilst the server/system uses 7.1. This is what "PHP Selector"/"PHP-FPM Selector" does. IMO, the current yearly price is well worth it, if you need that capability.
As standard (including CWP), you can switch to one particular PHP version, that applies to both the system and websites - "PHP Version Switcher".