Yes the V model is very different in overall design. Two different motors.

The slider on the muffler is part of the throttle control system. The engine of today uses a standard muffler and carb arrangement. You can replace the valve with a regular muffler and pressurize the tank.

5-10% nitor no problem. 20% oil is recommended.

I would use a 10x4. I like bigger props and less pitch.

Jeff G