I don't put smokes in kitchens or in family rooms that have fireplaces. I'll use a rate of rise heat instead - I'll put a smoke just outside the kitchen but not in it...each app. is different.
The 15P can use 2 or 4 wire smokes...use the 2 wire ones that way you don't have to muck around with power supervision relays...and of course you will use fire-rated wire.