Smoker or Sous Vide first?
Smoke first, then sous vide.

There are a few reasons as to why you could smoke first: 

(i) It has been shown that cold food/meat will take on smoke flavor better than warm meat (Source: AmazingRibs)

(ii) If you do sous vide and then smoke, you might risk overcooking the meat since the temperature in your smoker can run higher than your sous vide. Doing sous vide last helps ensure that you have a meat that is at optimum temperature throughout.

(iii) You'll smoke early and while the meat is cooked sous vide, you can prepare other dishes for the meal. Could be quite messy if its the other way round!

p.s the brisket sounds delicious! Have fun! :)