Help me set up my monitor speakers?

There is no audible difference between coax and optical S/PDIF. Use whichever one you have and/or is most convenient. Optical connections do allow longer cable runs, but that's probably not an issue for monitors.

Yes, that M-Audio page shows the most common configuration. All of the recommendations given there are excellent general guidelines. 

Bear in mind that while the equilateral triangle is the most desirable and widely-used setup, the actual distances vary. Larger speakers are typically set a little further away, smaller speakers a little closer. Given the size of your speakers, you may find that a distance of 2' or 2.5' works better than the usual 3'-4'. You'll have to experiment.

The most important thing you can do is avoid placing the speakers right up against a wall.

I started to write out a detailed technical description for testing speaker placement using test tones, microphones and SPL meters - and then thought better of it. We can always revisit the subject later. For today, let's keep it simple: just place your speakers such that they are the same distance apart as they are to your ears, and about the same distance away from you as your computer's display screen. Put a piece of carpet underneath them and you're good to go. 

(Note to other readers: before you suggest sand-filled speaker stands and MoPads and side absorbers, consider the OP's speakers' size and power capabilities.)