The paselas have pretty low rolling resistance - I've worn out a few pairs of these in 26x1.5. Sport contacts are faster, but heavier and wear out relatively quickly. I was getting less than 2000miles out of Sport contacts, and over 4500 from Paselas. Don't overinflate, just stick to the recommended maximum.

If you go from 1.9" big apples to 1.26", you might find the handling affected. that big a shift in tyre size will change the trail.

I would say that if you are on a stop start route you'll benefit greatly from a lighter tyre. Takes much less energy to accelerate.

OTOH, if you are mostly cruising on the open road, tyre weight doesn't matter so much.