I've been running a couple of bikes with just 2-4 gear ratios. No IGH. A very efficient setup. Variations of systems that were ridden and raced at the highest level over a century ago. Fix gears. One bike has a very long near horizontal dropout and can handle virtually any cog made with no changes in chain length. Another has 3 chainrings and 2 or three cogs (3 for mountainous rides, 2 for near flat rides.) Yes, I have to stop and move the chain or flip the wheel, even unscrew a cog and screw on another. Like the old days. Doesn't work riding with others who do not want to stop. But I ride alone, have no issues with the stops and love that I get to do every inch of the ride fix gear. And using those different gears, I can do the rides and the hills I love still, fix gear at over 70 years old.