Regarding waiting time for 1a/1b, personally, I got the invite in 2 day after the application, got the 1a result in the next day and scheduled for 1b. Got the 1b result after 1 week. Then know the Stage 2 scheduled after 2-3 weeks. And now I am going to have stage 2 next month. And I know they will tell u whether you pass stage 2 or not in the same day!!
My feeling is that they need more ppls recently so the waiting time ( both success/reject time) is much much shorter. Good luck to all!