Wider tires are not slower. They are heavier. Heavier tires are slower than light tires because they take significantly more energy to get them up to speed.
Yes, but the effect is rather small, because the rotating mass is small compared to the combined mass of bike and rider.
Also, a typical trick is to go to a smaller diameter wheel and a larger tire, so that the handling and moment of inertia are similar.
For example, I’ve got two rim brake wheels, one 700c 16 spoke aero front wheel with a 23mm tire on it, and one 26” 36 spoke tandem/mtb front wheel with a 44mm tire, and the difference in weight is 200g. (1200 vs 1400)
Even on the road bike, that’s only a 0.4% difference. (Not that they’re compatible wheels, it’s just the only decent comparison I have on hand)
But for most people, whether or not you went to the toilet before starting your ride, or had that bit of cake at the cafe stop, has a bigger impact than the additional grams on the tyres.
