reverse sear is great for bigger cooks and more temp control.
but you don't get quiet the same flavor from sear'n'slide - this is because searing first drips beef fat into the charcoal and that fat produces incredibly flavored smoke. That smoke adds amazing flavor back to the meat.
You still get a bit of this with reverse sear, but not nearly as much.
You can compensate for this by manually adding some beef fat to the coals while cooking indirect.
To get better temps from your thermapen, insert at an angle and try to keep it shallow. Wiggle a bit if temp doesn't appear stable.