Light pistons : start the flare / round out and by doing so the rate of descent will reduce. As you start to select the landing attitude, close the power smoothly so that you are at idle setting prior to touchdown.
Turbo prop : depending upon the type, you may well have in a hint of power on touchdown due to discing props. Depends really what the set up is. Close the throttles immediately when the back wheels touch. This was true of the Saab340. The AFM talked about close the power at 10ft. This would result in a firm arrival.
Jet : close the thrust levers prior to touchdown, otherwise the spoilers will not deploy ~ aka B.737
Mr Boeing says you fly it on with a small rate of descent; avoid floating and use up valuable runway.
The spoilers will dump the lift, put weight on the wheels, and braking will be effective.
You simply must not float otherwise the performance calculations are jeopardised, big time
Fly4Business : I would be interested to know which specific types of jet require power on touchdown. I presume we are not talking about the F14 tomcat landing on a deck?