You need to be in the area that the embassy has jurisdiction over for the submission of the application, after that you can travel around the country but be aware you can be called in for an interview, and Vietnam usually asks for a very specific proof of location.
just because you're not doing it, doesn't mean you're following the rules. The TM30 is to be filed every time a foreigner takes up accommodation no matter who owns it. If you ever need services from your local immigration office, welcome to the wake up call.
Every landowner must submitted tm30 when a foreigner stays there. You don't need to copy you just have to ensure that they file. A TM30 is always necessary.