"Some people use EAD(and terminate H1B) on purpose to save H-1B time so that if something happens with the current employer, they be able to pick up the remaining period of the 6-year H-1B limit through another H-1B approval with the new employer"---wrong
if you use EAD, you will atomatically lose nonimmigrant status including H1. then you can't change back to any nonimmigrant status in US any more. That is why so many people keep H1, not use EAD in case I-485 denied.(if you use EAD, you have to leave US as soon as I140 or I485 is denied)
you can use AP, which will not affect your H1 status. but can't use EAD
if you use EAD, you will atomatically lose nonimmigrant status including H1. then you can't change back to any nonimmigrant status in US any more. That is why so many people keep H1, not use EAD in case I-485 denied.(if you use EAD, you have to leave US as soon as I140 or I485 is denied)
you can use AP, which will not affect your H1 status. but can't use EAD