I’ll pass your request on to Mr. RR. He leaves for Viet Nam on Dec. 1. A business trip, but he hopes to take in some sights as well.
One non-FR site said that it is sometimes difficult to travel to former battlegrounds (which might indicate that less inaccessibile areas are available) and that you can rent car and driver for about $50/day.
This seems to indicate that travel is not very restricted, as there is no mention of need for a local gmvt “guide” to go with you, etc.