There are two kind of angiograms that I am aware of. One is a CT coronary angiogram, which is non-invasive. https://www.google.com/search?client=safari&rls=en&q=ct+coronary+angiogram&ie=UTF-8&oe=UTF-8

There's also a coronary angiogram that is invasive. https://www.mayoclinic.org/tests-procedures/coronary-angiogram/about/pac-20384904

To my understanding, both are reasonably accurate, but the coronary angiogram is the most accurate and is used for a definitive diagnosis of a blockage severe enough to require intervention.

I believe that often the first step is a nuclear treadmill stress test https://www.mayoclinic.org/tests-procedures/nuclear-stress-test/about/pac-20385231 or even just a regular treadmill test.

Which is prescribed first (or at all) seems (from my untrained perspective) to depend on the cardiologist and the CAC score.

@orionrex: As @nix58 alluded to, the number is an indicator, but it's not a direct measure. Poke around on these boards and you'll learn about people that have lived many years with scores in the thousands. Some have had interventions, but there's life on the other side of those too. The first step is to wait and see what your cardiologist suggests. When I got my high CAC score (600ish so not as high as yours) I was surprised and somewhat concerned at how slowly things moved. That appears to be normal. In your place, I'd read about the lifestyle recommendations and start working on those right away. It may make you feel in more control and it's something you should probably do anyway.