I would say that the devices visible on the upper surface of the wing are spoilers, they look similar to the devices on older gliders that I have flown. Spoilers have the primary effect of decreasing lift and increasing drag therefor increasing the rate of descent. Pretty sure it's the same for passenger jets but happy to be corrected. Once the aircraft has touched down, the spoilers are deployed to effectively reduce the amount of lift the wing generates ensuring that the aircraft remains on the ground, I can't imagine that they would produce enough drag to slow the aircraft much hence the reverse thrust and then the application of wheel brakes.

If you fly on the Embraer into LCY, spoilers are used to attain the 5.5 degree glide angle.