I usually cold smoke & sear smaller pieces on a charcoal grill, but when I hot smoke, I run a lower smoke temp than I would for whole birds, as I would with a butt or brisket in the 225-235* range.
For average size breasts (from a 4lb bird), I just dry rub and smoke for 1.0-1.5 hours depending on the intensity of smoke flavor your looking for. Small pieces take on a lot of smoke in a relatively short exposure time. Then, pan & tent with a pat or two of butter and a dash of lemon juice and sometimes a dash of soy sauce. This will add flavor and moisture in the container to allow them to steam for 45-60 minutes to finish, and, makes a tasty dipping sauce when served. Even if they get over done, they'll still be moist. White meat is not my best friend when it comes to smoking, but with this method it's hard to screw 'em up.
Single chicken breasts are pretty small to try and get an accurate temp reading in, so you can try to get 'em up to about 135-140* with a couple attempts to get a reading, then pan/tent or foil to finish. The problem with getting temp readings on several small pieces is that you've got the smoke chamber door open the whole time and losing tons of heat, so I choose to take temps after they've had a ride in the foil. You can grab the foiled meat out and close the door while you check temps, and not lose too much heat from the package you're handling if you have everything ready and close at hand.
I guess with one or two pieces, you could stab a prob into one and watch the temp on it while you're smoking. When it gets close, check the other one. I just have a hard time getting accurate temp reads on those smaller pieces, especially when the probe is left in the meat.
Hope this gives you a bit more insight before you take the plunge.
Have a great smoke!