Quality Wire

Like most of the construction materials and consumables in an automobile, wiring has to meet standards and specs.

Go with what the OEMs use. GPT is basic PVC auto wire. Cross-linked (GXL, SXL [hi temp]) insulation is best and a very small price premium over GPT. TXL is nice but not a necessity. Mostly used to save bulk in dash harnesses, etc. Teflon is only used to meet operating temp requirements in limited automotive applications, and in aircraft/missiles. (You don't want to be around if this stuff burns.) It is very thin and tough too, hence the special stripper required.

Battery cable has its own specs that follow primary wire pretty closely.

A lot of wire passed off as primary wire or automotive-grade has inferior standard PVC insulation. Don't spend the time and money to rewire with crap. Most of the quality automotive grade wire comes from a few manufacturers, Belden is a major supplier. Sources like Ron Francis, American Autowire, Painless, and web stores - all repackage someones bulk product at a massive markup. Buyer beware. Waytek, Mouser, and Terminal Supply sell to pro's and have good selections at trade prices. Generally 100' minimum.