Flaps 1 , 2 and 5 do provide some additional drag, not much but some. Flaps 10 is a substantial amount of drag.
No restriction on the 737 200, 300 or 400 re speedbrake and flaps but very unpleasant buffet at 10+.
In a low traffic density airport you can fly the maneuver speed + 10 kts and with planning it works out fine. Go somewhere busy and it changes. Reasons to go to flaps 1-5 would be for just a little bit more drag, which it does provide. But generally it is because you need to be slower or will need to be at flaps 10 or 15 soon for maneuver speed or additional drag. BTW the -400 had the 250 kt flap 5 limit as well.
The speed brake works poorly in this airplane especially at slow speeds. The gear is less disturbing to the pax as they are used to the wind noise and find it normal whereas the buffet from the speedbrake is unusual to them. Gear speed is 280 kts and still not that bad in the back. Unlike the 727 there are no gear door etc and big wheelwells that open and close during the gear cycle. Noise is worst in the cockpit from the nose gear.
The world of ATC sometimes requires different descent profiles than the sim. Even flaps 1 provides extra drag, just not much. It takes a long time to go from flaps up to flaps 5 as they move slowly (they are moving aft a lot though).
Like most airplanes there are many different ways to fly it, some work better then others and some don't work in some situations. As you fly the airplane you will try different ways to get it down and slowed down and see the difference. You will soon separate the theory from the real world on the line.