In my case I got my (Dutch) passport in Spain but it was issued in the Netherlands. Look at section 12 in EU passport: authority. That's what I filled in for my application.
You can take a trip anywhere in the country, you don't have to stay in hcmc. Vietnam is a big and beautiful place waiting to be discovered. I'm staying here for a month, got my approval and head back to bkk next week.
HCMC says 5-10 working days. If you submitted extra documents on 8 March, start counting from that date. I would not worry yet. A good chance you get it at the end of today.
One month should be fine for HCMC, they will ask for bank statements from the last 6 months and proof of income. I would advise to initially supply what is asked, they will ask for further documents at day 2 or 3. Just have them ready to upload.
Check on the consulate`s website what their turn around time for the visa is. Count from the moment you uploaded the extra documentation, not from the initial application date. I know it is nail-biting time right now, but as long as all your documentation is in order it should be fine. My nails are now starting to grow back again. 😂