Does this hose come with clamps or couplers?

This is the hose only. You'll need hose clamps (worm gear or band-style) and matching-ID couplers or barbed fittings to connect it into your system.

Can I use this for coolant, boost, and vacuum lines?

Yes, 3-ply silicone handles all three. Just confirm your operating temperature stays within the hose's rated range and use the right clamp tightness—loose clamps leak, over-tight ones can crush the fitting.

Does the 45-degree bend mean I have to use it exactly as-is?

The bend is pre-formed, so you've got that angle ready to go. If your layout needs a different angle, you can carefully heat and reshape silicone, but test-fit first to avoid kinks or cracks in the reinforcement.