Proper Way to PWM (Voltage Control) Dim LED Strip
The idea of PWM controlling LEDs is to drive them with their correct drive current for a proportion of the time and let the eye do the averaging as its response is in the 25Hz range.

Using a lower than recommended drive voltage produces a very non linear response and reducing the drive current can produce some unexpected results like spectral shift particularly if the leds are the multiple die types.

If you want to improve EMI then the first thing to do would be to reduce your PWM frequency by a factor of 10. Then you can think about softening the edges. A very simple RC filter would be sufficient.