Question 1: In-ears or wedges?
Question 1b: If wedges, one or two for the singer? (this is a cardiod vs supercardiod based follow up)
Question 3a, 3b & 3c) How big is the PA? Is phantom power available? Soundtech or mix from stage?
Question 4) Wireless?
Question 5) Does the singer also play harmonica through the vocal mic?
Question 6) Budget?
I will go on record as to how unpleasant an unappealing my recorded or amplified voice is to me. It not only sounds off, it sounds like somebody else. I
hate my voice through an SM 58; I think I sound less objectionable with an SM 57. To my ears, (for stage use), I sound most acceptable through the Sennheiser e865 condenser mic.
Finally, stage volume can make a decent FOH vocal almost impossible. Between too loud instruments, and wedge monitors blasting away, there isn't much room left to get the voice into the mic and out to the audience.
Take in the answers you get here, rent or borrow some mics from L&M, and try them out. You may find that the mic the
singer likes the best isn't what works best in context.