Travel to India during H1B Transfer while still remaining with old employer

[Sri N]

Hello,

Wanted to get advice on the situation described below - 

• I'm with employer A. My H1B visa in passport expired this May (2017), but have an approved I-797 till 2019.
• I have a job offer with employer B and they are ready to apply for my H1B transfer
• I have vacation left with my employer A, hence I would like to use it and go to India, use my vacation, come back and then resign with employer A to go join employer B.

Here are my questions:

1. While I'm in India on vacation as an employee of employer A, is it advisable for employer B to do H1B transfer in the background?
2. While H1B transfer is happening in the background, since I still didn't quit employer A, Can I renew my H1B visa with employer A via dropbox? (I have renewed via dropbox with employer A in the past)

Please advice.