As shown there are a lot of guidelines.
I keep my drill press at about 550 rpm and in nine years believe I have reset the speed less than six times. Works for me.
On the rechargable hand drills I have the trigger is the main speed control for screws and such. My DeWalt does have a shifter. I have to admit using the trigger to control speed for screws is tricky. Batteries are shot for my B&D screwdriver and I miss it. Replacement batteries are more than the screwdriver cost new and I'm too stubborn to buy more.
"Folks is funny critters."
Think for yourselves and let others enjoy the privilege to do so, too. ~Voltaire