My attorney received below email for H1B approval. Can I join based on this email (also USCIS status says approved) or do I need to wait for the hard copy of approval notice?
Assuming, this is an H1B transfer, you can join on the basis of H1B receipt itself.
If your concern is that you want to join only after approval, then yes, you can join now as you can see the approval online on USCIS case status website.