You should be using DOT4 in a performance car. You can replace DOT3 in any vehicle directly without worrying about having leftovers.

I use ATE Typ200 which has a 534 F boiling point. It also has good anti-corrosion properties. Spec'd by people who manufacture OEM brake calipers.

I am not aware of any OEM vehicle that comes with DOT5. My job is working on ESC modules and we don't allow DOT5 with our parts whatsoever.