I’ve seen a million in 100 dollar bills and I doubt it would fit into a briefcase, my guess would be about 750K if they were new bills tightly wrapped.
I saw the millions at the Fed in NYC, I have a friend that works there. They are stored in the gold vault in shrink wrapped bundles of 1 million. My impression at the time was that they were a little too large to be carried by tucking under one arm and if I wanted to abscond I would have to carry one bundle in both arms,