I think your pork loin came out that way because you cooked it at too high a cooking temp and that sealed the outside before it could absorb the smoke. Cooking on a drum you need to finesse the heat a lot more than what you are used to on the offset.
When I start the charcoal for the UDS, I will turn the starter chimney upside down and fill it, which means only about a dozen briquettes at the most. And when they are lit then drop them into a well made in the unlit briquettes in the basket. Stick the basket into the drum right away, and seal it up tight, with the one intake port uncapped, and the ball valve half open. Then wait to see what happens before you start to close off the intake. If you light too many coals to start with it will make some wild temperature swings while you try to get it under control.
I will also drop a refrigerator cold roast on the pit before it ever comes fully up to cooking temp. I figure that is the best time to get the smoke flavor into the meat. While it is cold and the pit temp is low.
I also mix the wood chunks into the charcoal when I fill the basket all the way through it in layers, making sure there are a few extra in the top layer that Ill be throwing the lit coals into to get heavier smoke early on.
You dont get much time to get the smoke into a tender and lean roast, so you have to make the best of the time you have. Dont get hung up on the thin blue smoke on the drum. You will see white smoke as the new charcoal and wood chunks get warm. Its not the same as workin* to get TBS on a stick burner
By the way, your pork roast looks terrifically juicy an delicious. My comments above are just to increase the smoke flavor. You nailed the temp and done-ness