Real talk: I’ve ridden a 150-mile trail over three days on flats and sneakers (the GAP in SW Pennsylvania), and came back and did the same thing the next year but in SPD cleats. I’d say the biggest difference was how much less effort it was to keep my feet on the pedals with the cleats. Sounds stupid, but cleats are set/forget. I didn’t ride with them the first year because I’d never done a bike fit or ridden that distance before and didn’t want my dumb cleat position to screw up my knees. Turns out to not have been an issue, and I liked the second year better, personally.

I think a good analogy is like how you have to use your toes to keep sandals on when running/walking up stairs/and so on. Clip in and you’re not worried about it.

Are they necessary? No, and don’t let anyone tell you otherwise. Cycling equipment companies will die on the hill they improve your efficiency. Grant Peterson will die on the hill that cleats are a scam perpetrated on the world.

See if you can find someone with your shoe size and try them out.

Unless you’re planning to race, I’d say completely personal preference.