PWM + switching power supplies

I have been moving into higher-power electronics projects and I am looking into if there are potential issues with using PWM-controlled power regulation through Mosfets when the power source is another electronic circuit such as a switch-mode power supply. Are there potential issues with drawing current from such sources at highly-varying rates such as at typical PWM frequencies (~1000Hz) ? I don't want to damage any power supply but I'm using up 100W power now. Thanks.

Switch mode supplies will have a fairly large amount of output capacitance to act as a charge reservoir. This keeps the output voltage stable throughout the whole switching cycle. If brief load pulses are causing too much of a transient drop, but the converter is capable of the average current output, you can add more capacitance.

Power supply decoupling capacitors are like the suspension system of a car; they work to keep the power smooth and level through all the bumps and jostles of an erratically variable load.