It will probably take something like an hour from plane touchdown to the time you walk out of the airport. If a lot of planes land at the same time there will be long queues at immigration. And it's a big airport, with a lot of walking.
There is no set route for the shuttle; it depends on where any particular car load wants to go. There could perhaps be two vehicles leaving at the same time, one taking passengers to the north of Jerusalem and the other to the south, for convenience. You might be the first to be let off, or the last, or somewhere in the middle. It's not inconceivable that there could - by some fantastic stroke of luck - be a whole car load going to that same area. It's unpredictable!