That's my understanding too that I'll need to carry both my passports for the entire duration of DTV and each time I enter the new passport gets stamped with 180 days
That's right, not issued as e-visa but as physical stamp in the old passport.
My question is if I can travel with both new and old passport and show the DTV in old passport to get a 180 day entry. That will help me save some time and can avoid a trip to Thailand embassy to transfer the visa to new passport before my travel