The front sight post can be removed, you just need to remove like two pins.
I don't think the difference in length between the two will make much of a difference at all. It isn't your barrel length but more it's barrel quality and your hop up unit / hop rubber which improves it.
If the motor is running at 9,000 revolutions per minute faster I would imagine that's good for rate of fire and better trigger response but I guess it could also mean parts wear out quicker and you would need to replace the gears with a high torque / high speed set earlier.
By the way, it's not a scope that comes with it, but a red dot sight. They're kind of different....sorry just bugs me a bit. Scope suggests it is a magnified optic.