3-2-1 too long for baby backs IMO. Baby backs I do 2.5 then wrap for an hour, sauce and maybe half hour, all at 250. Rub em with your favorite rub, throw em on, with a little apple chunk, I don't spritz.
Butts at 250 leave yourself 9-10 hours, they "should be" be done in 8 but they can rest for hours in a cooler for hours.
WRAP your butts tight, double wrapped, before they hit 160 and stall. Injection and rub a must, I also trim 90% of the fat.