wp nginx fastcgi cache vs wp super cache

Solution 1:

Your 30K number is likely irrelevant. In this question someone has 8 million files in a folder.

If you have many anonymous users you'd probably be best off with Nginx page caching and a CDN like CloudFlare (simple, with a free tier) or CloudFront. An anonymous user is any user who doesn't log into the website, o. It might be more accurate to say you can cache pages that aren't personalised at all. You can't cache, for example, account balance, threads started, etc, as they're different for each user.

FastCGi caching is what I call page caching. I have a tutorial that may be interesting.

Any Wordpress plugin means PHP needs to be started. PHP is slow and memory hungry. Nginx page caching means you don't invoke PHP, so it's much much faster. I would guess Nginx page caching 10 to 100 times faster than calling PHP, and uses significantly less resources - CPU and RAM.

Memcached is a fast key / value store, but it's typically callled from Wordpress so you still have the PHP overhead.