I did a QUICK search and didn't really see these answeres (which probably means I just missed them so apologies!).  Bunch of questions I know (I tend to overanalyze) but just stuff that's popped up looking at things in advance of the trip.

Cost: I’ve seen quite the variety of cost (which may depend on “source”, the next point). I often see $1.2-1.6M VND, but then I also see as low as $200K VND. I know the lower prices don’t include a room which you (have to?) get at “their” hotel for $100-200K VND. Something tells me price and “quality” aren’t necessarily proportional.  I'm also seeing occasional reference to USD.  For example, $1.2M VND OR $60USD.  Should I be bring USD (that's a great value at 1.2M=60)?  Is that HCMC only?

“Source”: Line, WeChat, and Zalo using the nearby function. Websites like kynu.net (which seems to redirect to cuclac.net now), timgaigoi.com, and others.  Is there anything notable about any of these, such as being scams or too overpriced?

Incall/outcall: From what I’m gathering in general it’s incall only to the girls hotel, but I also see some mention on forums of bringing the girls to the punters own hotel or Air B&B. Is it either/or in every case; will some girls insist on their hotel and nowhere else, but others not care? I was planning on Air B&B, but it seems they may always be in a building occupied by the host; is this a problem? Should I just get a hotel?

Available time: I’ve seen a lot of girls post ridiculously short (or maybe long?) times, like 9h-12h or 10h-3h. Is that really 10AM to 3AM, 10AM to 3PM, 10PM to 3AM?

Password: Some profiles I see online have a clear password (saw “Popeye” once?!?!). Others I only see the website. Is the website the password, are you suppose to find the password somewhere on the website?

Any knowledge of bisexual girls or at least willing to do FFM?  If so, any suggestions?

Lastly, processwise (think the questions above) is it the same from area to area? Do things work the same in both Hanoi and HCM or other areas?

I will try to answer the question that I can answer.

The password thing is when you message the WG/ WG manager you are suppose to text her the password that way they know what you are texting them about, instead of the off chance a complete random stranger just dial their number. If they don't have a password than you're suppose to text that the website number in place of the password for example "Kynu".

Line, WeChat nearby function work great getting WG since most of them will message if you first and they will que you a price and you can ask for video chat or photos before you agree to the meeting. I have a Vietnam trip coming up and even fake my GPS location to Ho Chi Minh City walking street area with Line to prepare for my trip. I got over 100+ WG information and price using the Line app. Zalo is like their facebook so must of the girls actually use that for their real life social stuff but for Line and Wechat those they use for work.

You're going to need a place to stay no matter what. You should book a hotel. AirBnB might be a few dollar cheaper but the hotel price in Vietnam is already very cheap especially compare to the western country. I suggest a Hotel but up to you.

Which is better? Paying USD or using the Local VND? Well this is actually very simply. Just take out your phone and google the USD to VND exchange rate and which ever amount is worth less at the moment just pay with that currency.

FFM? Well money talk so I'm guessing if the price is right you can book 2 at once.

Go to this website cuclac.net and use the phone number listed there to book the ladies.
Not advertisement.

HCM is the only city in VN I am familiar with in detail.  It has more hotels than anywhere I have been before.  If your hotel where you are lodging is not joiner friendly, just ask any cab driver to take you somewhere close and clean for a short time.  There are many small clean hotels for a romantic session which will only cost <$20 USD for the whole night.

Not sure if you misspelled it but there is an error message for cuclac.net. Maybe it couldn’t be reached from US.

Its been several years since i punted in vietnam, but i mainly did it in hcm.

I found there are two ways to do it. One is goto a ktv and the girls will go home withbyou after the session. Look up fortune ktv - its quite well know - the girls are not bad.

The second method if you are in vtn is goto the bars at night - you will come across a lot of working girls. Some bars are famous as a punter pick up bar. Apocalypse Now, is the most famous one.

I forget the prices - prob 100-200usd range.

I was in HCMC for a week back in January. Is it cool to bring a girl back to your hotel room? My hotel had a sign saying no guest/female guest. I don't speak Vietnamese so didn't brother asking when I was there.