The dome thermo will read higher, as the heat is pooling up there before it heads out the stack.
I usually split the difference between the 2 and call it good.
Many of us added an AMAZN tube pellet smoker for that 'extra' smoke. (especially when running at a higher temp for poultry, etc.) They work great, and don't take up much space on the grill.
Sounds like you are getting dialed in!