if your new employer is filing i-129 for you, make sure they check off "concurrent employment", rather than "new employment".
Concurrent employment allow you to have two TNs at the same time. (and file premium processing for faster approval and a fee)
if applying at POE, just explain the situation, be honest.
Don't resign from current job, until new TN is approved.
So I will tell them that the new employer is paying me a better salary package compare to my current employer and that is the reason of changing employer.
I may have to make sure that I will go to the POE atleast a week before the joining date of the new employer
Any possibilities if they ask me to resign first and than come to POE to apply for a new TN ?