Jeff, I have no experience with a cold plate as I have always used the tube smoker and ice no matter what smoker I use for the cold smoke. I think Kari uses a cold plate and has posted several times about it. I also like Dave’s method he mentioned.
To answer one of your earlier questions regarding which tube smoker to get...the 6 inch will smoke for 2 hours, the 12 inch 4 hours. I believe I have that right, if not someone please correct. Good story about customer service, my first tube smoker was a 18 inch. (Not sure if It is still available) I communicated with Todd and he suggested I cut and make a 6 and a 12. He (Amazen) sent me the extra end caps I would need to make the other. Awesome service you never forget.