Oh this is a fun one!!
Everyone has given you great advice above. I see what you are working with and know what you are trying to do. What I can tell you is there is a ton of variables to getting bark/good bark. Surface texture, surface temperature, surface evaporation, time of cook, temp of cook, time of cook, fuel smoke production, etc.....etc.....etc....etc.....
All that being said....If I was working with the same cuts that you worked with I would try everything already mentioned above. I would also do the following....
1. Prep I would heavily season as some has said above. Black pepper is your friend. Maybe try something like Hardcore Carnivore Red Or Black (would use red on a butt. Either way I love this stuff. Look it up) Use some yellow mustard or another binder to help keep that seasoning on as long as you can since the smaller pieces will mean that temp will come up faster than a larger cut of meat. BUT most importantly...STICK all of that in the freezer for about 20 minutes before you take it to the Smokefire. The lower surface temperature will be your best friend to help with smoke retention/ring and slow your cook down a bit so you can work on bark. Finally you can also add a LITTLE sugar to your rub to help with caramelization.
2. Cook. Start well below your above cook temp. For smaller cuts I would start out at 200 for an hour or maybe two and may also try smoke boost. I would also stay on the low side for the rest of the cook to around 215 to 225. That will increase the time for surface convection which will not only increase bark but it is literally the engine that drives the car from turning that tough cut of meat into a delicacy (do not let anyone tell you different....yes the fat will render but it is the surface convection and evaporative cooling that does all the work and until that is done........the meat is not done...)
3. Moisture. Your cook seems sound. However I WOULD spritz a liquid of your choice every 30 minutes for the first 2 hours of your cook. Especially for the first hour or two at 200 degrees or during smoke boost.