It is Cd that peaks at transonic speed, not drag. The the measured and documented 80 NS record is Mach 1.42 with an AT F80. Even the old AT G60 could go supersonic, not faster than the G80, but carrying instrumentation. The AT G80 is actually more like a G100 with a thrust tail that lowers the average thrust to a modern legal MR motor. The AT G80 is the way to go for max speed or Mach with a model rocket motor.Drag increases hugely with velocity and is maximum at transonic speeds. You (the G80) don't have enough thrust to punch through to supersonic and keep it there. So yeah, the second motor also does nothing. Most likely, with those ridiculous tiny ineffective fins, the vehicle will suffer transonic instability and fall apart. Look really carefully at those graphs from the simulation, they're talking to you.
The Nv7 design is another matter. It is rather heavy. I would suggest starting with the Apogee Aspire and reading all the anecdotal reports of other rocketeers. Two stage might be fun to sim, but is absolutely nuts if you want observe or measure supersonic MR performance.