Aria Vent Inc. Flushmount Pro (4" x 10")

Bought 7 vents covers for my remodel (4x10 and 4x14). They are 1/8" - 1/4" too big for my 10x4 registers can't be inserted. Any suggestions?

How do you control the air flow?

Since this thing appears to block about 70% of the duct area, where does all that air that can't get around it go?

Does this work with vinyl laminate flooring ok? I have a wood floor that already exists, and I'm putting the laminate over it