Thanks everyone for suggestions!
As for weight, I weigh just over 150#, the bike is somewhere around 25#(it's a guestimate, specs say 21ish, add the rack/bag/bottle on top of that), so probably on the light side, which means 25mm might be fine? Is there any 25mm tires with decent tread for more traction? FWIW Currently I'm using 25mm Clement Strada LGG Road, the tire that comes with the bike.