H1b visa transfer + 60 day rule

Hi, I work for employer A under an active H1B petition. I have a new job offer (employer B) where I will be starting on receipt notice from Aug 15. Employer B is going to file for my transfer via premium processing on 8/8. I would like to give notice to employer A tomorrow.

Is there anything they can do to hamper my employment for employer B? If, let’s say they retaliate and terminate my employment I would still have 60 days grace period as per the rule, correct? And I can work for employer B as soon as I get my receipt?

And once I start working with B, I would have another 60 day grace period were I to lose my job with them, is that correct?

Basically want to know if there is any risk in giving notice before transfer petition has been filed.

Yes. However I would advice resigning after your H1B is approved just to avoid any unwanted situations.