Multiple H1B petition filing

Hi All, @anil_am22, @Kalpesh_Dalwadi
I have few questions. I am working for Employer A. My I-140 is approved and its more than 180 days since approval. My current petition is valid till next year Dec 2022.I was looking for job change and recently got job offer from Employer B. After accepting the job offer, they just filed my H1B change of employer. Meanwhile i also got another job offer from employer C.
Due to visa uncertainty i want to start H1B process for both and chose employer C in the end. Employer B already filed H1B in premium processing.

  1. What if employer B 's H1B gets approved and i joined employer B while employer C has not yet filed the H1B or in filing process. So will that change in employer affects the visa process of Employer C?
    OR Employer C can still file H1B change of employer on the basis of H1B petition from employer A ?
  2. Do i need to inform Employer C about this job change ?
    I don’t want to wait with Employer A thats why i want to join Employer B while Employer C is preparing documents.

No.

If you already joined employer B, you will include the most recent paystubs from employer B along with other supporting documents when filing with employer C.

You don’t need to but eventually they might know from the documents you will submit with your transfer application. Many times beneficiary work directly with the employer’s immigration lawyer for supporting documents so employer B may never know you changed the job. In any case it should make any difference to the hiring employer.