if you’re a real newbie to linux, there’s no harm in using a distro like TrixBox to get started. once you have a working system, you’re much more likely to enjoy it and want to get under the hood. then you have a choice, either working with FreePBX or without it.
my home Asterisk system started life as a ClarkConnect box with an A@H tarball install over the top. it doesn’t look like it now, but i had a working system in an hour, and haven’t looked back.
edit: when i say it doesn’t look like it now, i mean it doesn’t look anything like an A@H install !! it’s now a fraction of the size, faster and a lot more functional.