Welcome to the forum Troy, lots of reading a nice folks happy to pass on good advice and tips.
With the entrance of the of a Flow Hive2 as it is made there is no restriction at all to the queen or a drone which is a bigger bee in its width.
Most bee keepers restrict the entrance further for a few reasons, to make a smaller entrance to make it more defendable against attack or reduce the cold air flow onto the brood.
This is what I use. The metal entrance reducer is called a ‘mouse guard’. Here I use them as a ‘Cane Toad guard’. It can be removed and fitted upside down to lock all the bees inside but still gives good ventilation if you want to move the hive.
Each entry is 1/4" (6.5mm) wide and 3/8"(10mm) height, that is plenty of room for a queen to go through for her mating flight or when swarming. Drones are even wider than a queen and they can walk thru as well.