As a Dreamhost user, I can set my domain to use any of the following:
- PHP 7.1 CGI
- PHP 7.1 FastCGI
- PHP 7.2 CGI
- PHP 7.2 FastCGI (Dreamhost's default)
- PHP 7.3 CGI
- PHP 7.3 FastCGI
From a (very) quick search, it seems that PHP 7.3 is tends to be faster than the previous versions. And when it comes to backward compatibility, the official PHP website says this: "As long as you don't have any heredox/nowdoc string litrals that contain the same token as the first positive character in a line, you are golden."
On the Automad website, the permission instructions page mentions that folder permissions don't usually need to be bothered with because most hosts use FastCGI. That's the only mention of any of this that I've seen, and it doesn't actually mean that FastCGI is better overall than regular CGI. "Fast" sounds like a good thing to me, but you're the expert.
My guess is that this doesn't make a big difference. I'd also guess that if someone had to pick a winner, PHP 7.3 FastCGI would come out on top. The third guess I'd make is that Dreamhost defaults to 7.2 instead out of an abundance of caution regarding compatibility with as many things as possible so that they get as few support tickets as possible.
So, given that it is trivially easy for me to pick which version of PHP my domain will use, is PHP 7.3 FastCGI what you'd recommend for the domain with which I intend to host an Automad website and nothing else? Is there any reason for me to not use that version?