What is the login for Arch Linux?
There is currently no user account for you, so (this time only) log in as the generic administrative user, "root". If you used the prebuilt image, the password is also "root" (we'll change it in a few minutes); if you installed it yourself, the password is whatever you set it to be during install.
What is the default username and password for Arch Linux?
Actually, there is no default user for the os. You can try root without any password and it most probably will prompt you to create a user. It might be that your VM created a user for you.
Is Arch Linux insecure?
Yes. Completely safe. Has little to do with Arch Linux itself. AUR is a massive collection of add-on packages for new/other softwares not supported by Arch Linux.