I noticed that there was the i386 and X86_64 versions. Now, I have an AMD3500+, so I thought about the 64 bit version, but I heard that the i386 version is overall a better choice due to increased compatibility.
x86_64 are for 64-bit processors while i386 version are for 32-bit processors. If your processor is 64-bit, you can choose x86_64 or i386. AMD's 64-bit processors are fully compatible with 32-bit OS. That means you won't have any trouble running i386 version of fedora (or any i386 linux distro) an AMD 64-bit CPU. However, x86_64 versions of fedora (or any other x86_64 linux distro) will not work on 32-bit processors.
So you should first check out if your processor 64-bit. The safest bet is to use i386 version.
BTW, I have no idea about your other question...may be someone else can tell you more.