However, the RAM footprint of the Nginx+php-fpm set up is considerably smaller than the large Apache prefork configuration I had originally, and the CPU utilization while servicing a dozen or so ...

Here's a quick tutorial on how to setup Nginx with PHP support. The key? The installation of fastCGI, aka PHP-FPM, so Nginx can serve PHP files to clients.

Hestia is a web-based GUI for configuring NGINX, Apache, and PHP-FPM. Jack Wallen shows you how to get this up and running on Ubuntu Server 20.04.

If you're building NGINX sites, you'll probably need PHP-FPM support enabled. Jack Wallen shows you how.

Engineer straykerwl has reported test results that using NGINX Unit when running a PHP application improves response speed by about 8 times compared to using PHP-FPM.