Cpanel? Been using it for years. Great.
Scripta? That's just an installer for various different softwares such as the invision board, phpnuke, etc. The host (whomever it is) usually do not provide any support. They provide scripta (aka Fantastico) solely as a convenience for you. Do you need scripta to install the other software? No. Those software are all free programs available on the internet and most have their own install script. Again, the host that has scripta only provides this as a convenience, mainly for novice webmasters. Drawback? Biggest one is you don't know which version of software you are installing until you've already installed them. Really no big deal though.
Webmail: You should have a POP3 with any account. You can use Outlook, Netscape Mail, Eudora, etc., are all mail clients usually ran off your main PC or Mac, etc. Webmail is just so you can go anywhere in the world and access your email using any browser such as IE, NN, Mozilla, etc.