Hello, one thing cannot go without another, for every action you must counteract, due to the position of the engines, in this case as the are below the wings, if you increase thrust the plane will tend to pitch up, therefor you must pitch down and the airspeed will change. If you pitch down the aircraft will tend to increase the speed, therefor you will have to reduce thrust. Another thing to consider is the wind direction and intensity. Also the weight of the aircraft, amongst many other factors, so no two approaches are ever the same. While on the Glide Slope, the normal glide path is 3 degrees (Bucharest Otopeni is 2,5 degrees, so when you see the video of that approach you could see it to be more shallow), every flap setting will adjust the pitch and thrust required to maintain the path, and at flat 30, which would be the standard setting for a 737 on final, it will require approx 57% of thrust to maintain the speed, pitch and path. I hope this helps
