to froggy
In my case I got EAD and AP first.. One month after getting EAD only I got i-485 receipt.
This is because case numbers (EAC) of i-485, EAD, AP are different and they may go to different officers and they may have different queues.
regarding FP notice as others mentioned it depends on local office. If their workload is high you have to wait sometimes 6-7 months.You can see RD and FP dates in rupnet.com/immigration. Some got FP notice in 2 months , for others it took even 8 months.