You don't have to use them. If you use EAD, you lose your H1 status. If you use AP, you can keep your H1/F1. Technically you can't have H1 after you use AP but many people are doing this and still hold H1 status.
If 485/140 is refused, you can renew EAD based on motion to reopen the case, or you can pick up the rest of your 6 year H1B, excluding the time period you have used your EAD.
There are no crystal clear rule/bill/memo for this issue, but people are doing it everyday.