YMMV, but yes. The two plates are there to keep the gears in the same position relative to one another. If you can do that without 2 plates, you’re accomplishing the same task.
2 standoffs are enough if they make the gearbox stiff enough. If the plates are bigger, thinner, or further apart, you may need more. If the standoffs are smaller, further apart, or longer, you may need more.