As it read in the voucher which I got after booking, there was a message on my email aboutpick up time for bus. The driver was accurate at the time indictaed ad explained that he first would drop in all other tourists at termanil 2 since they had earlier departure time, and then he would drop us in , at terminal 1. The transfer costs are not high in comparison to taxi.
As for each shuttle bus: you don't get ride on your own, but with many other people, that's why the transfer to destination point can take you up to 2 hours. If you save your time, you are recommended to take private transfer.