My wife and I are on H1B and her extension got an RFE recently ans now a days her employer is reluctant on even responding to RFEs in some cases. We do not recieve the RFE details yet but thinking to have a back up plan by filling H4+EAD. My questions are:
1. Can we file Change of status H4+EAD in parellel to current H1B petition that got RFE?
2. If we can file the change of status H4+EAD in parellel will that have any impact on current H1B petition (if employer choose to reply RFE or refile) or Vice a versa?

Thanks in advance!
You can only have one status at a time. If you have two concurrent nonimmigrant applications, whichever one gets approved later will supersede the other.

If your wife's I-94 is still valid, she can file for COS & I-765 concurrently and ask employer to withdraw the H-1B extension. If it's expired, then forget about it. The H-1B extension would need to be approved first before any COS could be granted.