Will this hose work with turbo boost and coolant systems interchangeably?

Silicone handles both high-temp coolant and positive boost pressure. For boost applications, you'll want stainless clamps rated for the system PSI. For coolant, standard worm-gear clamps work fine. Don't mix duty cycles — once it's a boost hose, keep it that way.

Do I need anything else to install this, or just clamps?

You'll need two hose clamps sized for your tubing diameter — one on each end. The reducer itself ships ready to install. Test-fit before clamping to make sure your piping alignment is clean.

Can this reducer handle sustained high pressure, or is it just for flow transitions?

Three-ply silicone is built for sustained pressure in both boost and cooling circuits. That said, always verify the pressure rating matches your system's max PSI — oversizing the clamps or running above the hose rating creates a failure risk.