If you find a job in a short period of time and you file H1 transfer, your H1 may get fully approved with I-94. In this case, your status will be H1. But if you do not get I-94 with your H1 approval, just forget about H1 and use EAD to work. I do not think there is a problem for your I-485.
In the worst, you still can get your H1 status back by going out of US to get an H1 visa afer you use EAD if your I-485 is denied.