doing my due diligence before my first time.  for my question "good/safe/best" is in regards to avoiding LE; not service, price, looks, health, etc.

That's the point of the TER rep. There is no guarantee, however it sounds like you are doing your due diligence to minimize the risk. Only other thing you can do to reduce risk is setup the date as an outcall, but from what I'm reading, you are as good to go as you can be.

you are 99.99% "safe."
Regarding who sees the form, could be a booker or her.  I suppose you are concerned because you provided personal info?
If comfy providing personal info to a well-established provider for screening, then I don't think the means of transmission of that info makes that much of a difference.

I want to see multiple reviews by hobbyists with multiple reviews of providers with multiple reviews, decreasing to nearly zero the chance that anything is staged, and then I might also PM a couple to ask if there is anything I should know that they weren't comfortable including in the review. This is an abundance of caution and I'm sure many would tell you unnecessarily stringent, but it's how I go into an appointment with no worries whatever, which means I have a better time.

...however, you can minimize your risk to acceptable levels.  In this case, it appears from what you have described, that you should be good to go. Both gals have multiple reviews by reviewers who themselves have written multiple reviews. The chance that either one are LE are very slim indeed, in fact, if the the reviews are good, the chances you'll have a bad time are also very slim. Relax and enjoy the journey.

To further reduce your risk, it might be safer to arrange an outcall instead of an incall. If they are Preferred 411 member then it's an additional safety measure. Since it's Vegas, there are quite a few providers who show their face clearly. I feel safer to book an appointment with them, especially if they have nude or semi nude pictures. As a last measure, you could contact other reviewers, who have more than 5 reviews and had seen the provider recently, to make sure the provider in question is legit. None of them are really necessary, IMHO, but it should make you feel safer. I don't feel any leo will spend that much effort to just nap 1 or few hobbyists. Once you book an appointment, you should just relax and enjoy the experience. I am sure the ladies will take good care of you.

a review of the wonderful lady you spent time with.  

LE concerns, then you will most certainly enjoy your experience more.

thanks, after putzing around here you pick up on the themes quickly.  i know there are no guarantees of course.  i am planning an outcall, 3hrs (figured time will fly).  i will say i made some minor mistakes in my initial contact with these providers but i'm moving forward.  my trip isn't till the end of the month and i was told to re-contact with 1 week to go to confirm, this doesn't seem unusual.  last thing is going to pick up a burn phone and hope i don't get canceled on :-T

hear from lady A, at least you have an idea of what direction to proceed.  Don't actually schedule lady B but have her contact info handy.  If time becomes short and you haven't heard from lady A, then you will be all set to proceed with seeing lady B.

and it's good that you realize that there are no guarantees in this enterprise.  But from your description of the providers with regard to the reviews, I'd say they are probably safe.  No, it is not likely that your email/website forms are going to someone other than her.  An exception might be if she has someone who handles all her bookings, many do use assistants to handle that.  Hopefully, she will do her screening of you as well.