Popping noise

It is very beneficial to block the the cross over, you will see a decent pick up in torque.
The engine will warm up about same pretty much, but the intake charge being colder now could make the fuel seem a lil less atomized and maybe give that lil delay to it when leaving the line.

But speaking of valve overlap...it is never a good thing for performance/efficiency to contaminate a cylinders intake charge with anothers exh/farts. lol