"Apache is working on your cpanel server"

When you type the ip rather then the fqdn of a website (which gives you the actual website your going for) and you get the default apache "Great Success ! Apache is working on your cPanel® and WHM™ Server"

screen on the server what exactly does this say about the security of the server / website?

It tells you that there is a probably a virtual host on the server, but what else does this say about the server?

Can you possibly find any default files on the server to possibly get a look at settings etc?

When you see this does it mean anything?

It doesn't necessarily mean that the site is vulnerable, but if it displays version information you can search for it in vulnerability archives and see if the current version is exploitable ;)

Actually, freshly, out-of-the-box installs might/probably have (perhaps) exploitable default configs.

Anyhow, default configs.