Two Pay-slips For Same Duration. Help Me To Understand On Potential Concerns.

[infodigger]

Scenario:

I am on H1B(I140 based) with EmpA. Currently on EmpA paid long vacation. While on vacation, I have applied another job in job portal and got a better offer with EmpB. Now EmpB filed H1b Transfer and it is approved now. So now i have two approved H1Bs with two different employers. As EMPB offer is good one, I would like to choose EmpB. As per my knowledge, I need to resign the job with EmpA first and then only will join with EmpB. So subsequently i will miss my paid long vacation. 

Need Help On Below Questions:

Q1) Is it legal to join with EmpB without resignation to EmpA? Not working for EMPA now and during vacation time.

Q2) If answer is 'YES' for Q1, Then I will plan to put resignation for last vacation day as my last day with Emp A. So that i can get my benefit from EmpA in payslips. Down the line I have to face any potential issue due to this? Because theoretically two payslips i get. Please let me know.

Q3) If answer is 'YES' for Q2, I will resign EmpA first and then only will join with EmpB. But curious to know what potential issues i will face in my future. That will be at stages like, H1B extensions from EMPB?/H1B Tranfers to EmpC?/GC/Perm filing from EMPB?/I140filing from EMPB?/GCinterview from Any employer in future? Please point the stage.

Q4) While browsing answers for above questions, I have found an interesting tweet. Please see below link. Does it mean, YES for Q1; and NO for Q2; can show proof of my vacation record at any potential stages mentioned above ? Please let me know. 

Thanks In Advance For Your Time and Help.  

[gopalakrishnach]

Q1) Is it legal to join with EmpB without resignation to EmpA? Not working for EMPA now and during vacation time. .. You ahve to resign from EMP A and then join EMP B. You cannot work for 2 employers at same time.