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Let's begin with the brisket. Given the size, they're probably flats...the longer piece of meat that sits under the point. When they're fabricated as one entire cut of meat, they're referred to as a packer.
I've never smoked in a water cooker but the principal is the same. The flats are done when easily pierced (in & out) with a probe or skewer. This happens in the 195-205 temp range...usually right around 200. We've all learned to cook "till it's done" vs exact times. Rule of thumb, you'll need about 1.25-1.5 hrs @ pound for your flats. Keep a probe thermometer set in the smaller of the two, or better yet use 2 thermometers. 5-6 hrs will probably be needed.
Top Sirloin roast...a beautiful cut of meat that is best served medium rare, which means an internal temp of 130. You'll want to monitor the internal temp as you go. Best guess for time? 2 hrs. Once you hit the 130 mark, wrap your meat in foil and hold it in an insulated cooler, wrapped in a towel. The meat will continue to rise in heat...maybe 5 more degrees.
You can also FTC (foil,towel,cooler) your brisket as well. ALWAYS allow large cuts of meat to sit at least 30 minutes to allow the juices to settle.
You didn't mention a cooking temp. For the purposes of this discussion I'd suggest 225-250.
Good luck and let us know how it turned out.