I can't estimate how many string choices there are out there, but it's a big number.
I listen to jazz players, especially the old school ones, who use flats. Surf music commonly involves flats. They sound great. I tend to use the hybrids (Brite Flats and Half Wounds). They get rid of the squeaks well enough and are brighter.
I am well stocked with different string gauges and windings. I can't settle on anything really. I've made peace with that realization.