Passport with a Vietnam Visa. Make sure you have more than six months left before your passport expires. Get you visas at https://evisalegal.com/vnm or go to a Viet travel agency.
Bring an unlocked phone and use an eSim. My favorite place to buy is (https://agoda.voyeglobal.com/). Get unlimited plan for two weeks for around $30. Download and get it prepared so that you can turn your regular Sim off and turn this one on. That way, you will have internet as soon as you land in Vietnam, which is needed for transportation.
Download the Grab app, which is Vietnam’s Uber. Add a credit card that has no foreign transaction fees. Use Grab to travel everywhere. I recommend upgrading to a big ass van (about $5 more) for travelling over an hour since they have AC in the back.
No, just go to both. Quit being a bitch.
Yes, use Grab to order food like DoorDash. Don’t pay in advance. Give cash to the driver because restaurants tend to run out of food.