The TenderQuick is for the faux smoke ring only. It is not for taste, just for looks. It is not necessary, but it's easy to do and fun to play around with. I'd be careful with it though. Doing the TenderQuick step too far in advance can produce a smoke ring so large that it starts to look (and taste) cured. Even though the cure gets rinse off, the cure that's already been absorbed continues to work it's way further into the meat over time. So I personally would not recommend the overnight in the refrigerator after the TenderQuick. If using the TenderQuick for a faux smoke ring, it's best to apply the TenderQuick, rinse, apply your binder and seasoning rub within a few hours of going into the smoker. I have not noticed a big difference in flavor with brisket between applying the seasoning rub the night before, or shortly before smoking.
Most people also go 225 for brisket, but you'll just have to decide for yourself. If you have the time, there is no disadvantage that I'm aware of smoking at 225.