Question How to specify UNIX sockets

[Zoo3]

Server operating system version

CentOS 7.9

Plesk version and microupdate number

18.0.46

I operate Nextcloud(It is not a Plesk application) and I'm currently rechecking my configuration.
I have specified "fastcgi_pass php-handler;" in nginx additional directives. Then I create nc.conf in /etc/nginx/conf.d and write upstrem in it.
Is this approach correct? Is there a more Plesk-like, Plesk legitimate way?
Suppose Nextcloud is operating under a subdomain called NC-DOMAIN.

upstream php-handler {
        server unix:///var/www/vhosts/system/NC-DOMAIN/php-fpm.sock;
}

 

[Bitpalast]

What is the purpose of the directive? If you want to use Nginx, why not disable Proxy mode and choose the PHP via Nginx handler in the PHP settings?