I have done a few racks now using the 3-2-1 method and have tried different things. I usually default to hickory for my smoke, and have tried a chunk or two of it for the last hour and they came out very smokey, which is not a problem for me. I have tried them with no smoke the last hour, and they were still excellent. The best ones I made though, had Hickory in the beginning, then the last hour I used a milder fruit wood, and they came out great. I used Apricot for the last hour and it added some smoke, but a little sweetness as well.