According to analysis from engineers, or Esther from a guy I used to work with who studied break waves for the state transportation board, less cars with larger gaps is better. That's why you see semaphores on highway entering ramps sometimes, ie 101 around SV or certain European big city inner highways.

This is a problem that can probably be solved someday with self driving cars collaborating to make highways huge coordinated conveyor belts.

Seattle adjusts the speed limit on one of their highways down to 45 or 35 during rush hour which increases the throughput as the cars can be closer together. Not sure if that has been picked up by other cities.