When to withdraw H4 application with H1b PP transfer initiated

My position was eliminated in the organization, and was out of employment for more than 60 days. Applied for H4 visa in between as my spouse was working on H1b.
I’ve recently accepted a job offer and my new employer filed for my H1B in pp and received receipt notice for the same, as i’ve been working for more than 8 years in USA with valid I-140.Please let me know

  1. When to withdraw COS [ H1 to H4 due to grace period over]
  2. Is it ok to withdraw the H4 application prior to H1B approval as employer is requesting the same

Looking forward to hear back.