no you can not. But you can always use rendered movies of particle systems inside After Effects. You can also navigate to motion library and use shapes for particle systems in AE. AE have good tools you only need images to make particle systems. I also suggest you get Trapcode Particular 2 for AE as it is the best particle system around.
Please understand that DRAG behavior is a separate behavior that can be applied to emitter. select your emitter then go to behavior, select SIMULATIONS and use DRAG. I should have been more clear how you apply Drag behavior. I hope this helps
Use DRAG behavior to slow down stars. Apply it to the particle emitter. Use Amount slider to see the effect. Also use Z if needed to pull objects in Z space.
I hope this helps.
Optical Flow has tendencies to create artifacts on a footage, but I have not heard that your playback suffers. Am I correct in saying that you are talking about playback of your video.
render your animatin with animation codec rather than 422 codec. If this doe snot work please delete your preferences and render again.
Let me know how you get on.