i'm mostly a bass guitar player, but i was playing upright for years in the past... and i love effects.
as far as the type of strings... can't help. start with the cheap ones and hope they work, i guess.
regarding distortion... just remember that arco is much louder and "higher output" than pizzicato, so you may want to turn down the "gain" or "drive" knob on your pedal when bowing. unless, of course, you're going for an over-the-top type of sound, in which case get a fuzz.
also: you may want to wander over to the Effects forum in the BG area. LOTS of fun there!
sorry i couldn't be more help on the string question...