Wow that's some racket for sure.
That sounds like it's something in the top end of the engine, or in the tensioning system for sure. I'd be pulling the valve cover to inspect for sure. Collapsed lifters don't usually sound like that.
Rod knock usually happens at a certain RPM (which can be different in each case) and is easily repeatable...your's obviously makes sounds, but it seems to varry
Here is a great video of an SR with rod knock
SR20 GTiR rod knock - YouTube just to give you an idea of how it sounds.
Good luck, hopefully it's a simple procedure and not long term surgery!