Coating - Airless Spray

At the pump or at the nozzles?

Assuming your machine can keep up with two guns, you should be fine.

One sure fire way to know for sure, would be to hook it up and try it.

With an airless machine, there is always a variation in output pressure at the gun tip, and the pressure goes up and down within the lines as the machine pumps. The question is, will it interfere with the proper atomization of the paint?

We do this all of the time on the one line. In order to have good control you will need to install a separate material regulator on each on the different guns using a different dip size. You then can adjust the fluid pressure to meet the needs of the tips properly. That assumes your pumping system is sized correctly.