With the Neo-moto 2.3 there will be virtually no tire clearance change going to a 35mm wide rim from any smaller rim width. Because the knobs will remain the widest section of the tires. In fact the more "square" profile of the Neo-moto 2.3 with the wider rim actually makes the widest point of the tread slightly narrower. I've measured the difference, it's about 1 mm narrower on my P35 compared to the same tire on my 28mm Blunt rim.
The air volume increases so you can use much lower air pressure for a smoother ride and bigger tire patch. And the more "squared" tread gains edge grip when cornering.
Using the same tire with a wider rim, there is a little slower rolling resistance on smooth hardpack form the bigger tire patch, but less rolling resistance over gravel, sand, loamy, and rocks from lower pressures and bigger tire patch.
The air volume increases so you can use much lower air pressure for a smoother ride and bigger tire patch. And the more "squared" tread gains edge grip when cornering.
Using the same tire with a wider rim, there is a little slower rolling resistance on smooth hardpack form the bigger tire patch, but less rolling resistance over gravel, sand, loamy, and rocks from lower pressures and bigger tire patch.