Because the grip pattern may drag on the snow, a no-wax ski is difficult to skate with and is generally slower than a waxed ski. But, when you stand on one ski and press down, the ski has to bend enough to let you grip the snow and move forward. Your weight and skiing ability affect the amount of camber and stiffness you need. Stiff skis are faster but more demanding of your technique. It takes practice to avoid slipping backwards on stiff skis.
Racers love stiff skis.
People who ski on groomed trails use a narrower ski than backcountry skiers. People who ski with heavy packs choose wide skis. Skis are hourglass shaped, narrower under the foot than at the ends. This is called sidecut and it makes the ski easier to turn and steer. Backcountry skiers need skis that turn easier than a skier who is always in prepared tracks.