My Hybrid has 21MM wide rims.
I'm running 26MM tires, but I wouldn't go narrower.
When I wear out the rear, I'll probably go to a 28MM and stick with 26MM on the front.

My previous tires were 35MM Specialized 105 PSI tires and the rolling resistance was horrible in addition to the heavy weight.
Smartest move I made with that bike was skinny tires!