Is it better then OpenLiteSpeed and the WordPress plugin LiteSpeed Cache? It could be used for more than WordPress. But you could use the good old slow Apache.

But how do you not cache when people are logged in? Otherwise, it'll show the entire admin interface to non logged in people. Maybe write a post, how to incorrectly configure Varnish for WordPress.

Something I found, doesn't mention SSL. So how do you use it with SSL?

Not great for DirectAdmin. It's better if you are configuring/managing the server the not lazy way.

Maybe the SSL is on Varnish. So the server probably only listens on regular HTTP. Wouldn't work for shared hosting. Or DirectAdmin. DirectAdmin could possibly add support for it though.

But if you have to configure Varnish manually, you might as well not use DirectAdmin.