ya the angles still matter, any time your using halftone dots you want to avoid moiree so using an angle around 22degrees is a good idea. use the same angle for each color as you will idealy want each dot to fall into the negative space of the other color.
For 2 color jobs i often prefer to do my halftones in photoshop. I do this so i can punch out the halftone dots of the top color from the color underneath so my dots are exact.
my recommendation when doing this separation (no RIP needed for this)., focus on creating the black channel, make a new document to work from and create the bitmap halftone, convert back to grayscale so you can copy the channel back to your original working file. You can make the purple channel simply by convert it to grayscale, adjust levels so your solid purple area becomes 100% black (make a copy of the document to work on). Convert to bitmap and create your halftones, then convert back to grayscale. Now you copy this channel back to your original document and punch the black channel out of the purple.
