Val,
I completely understand that finding someone in a similar position to you can be an inspiration and hearing that Hairenough is getting along well since wearing hair is helping you.
But, matching point for point doesn't mean that you'll necessarily have the same experience, just because you find similarities.

You'd have to have matching DNA, temperaments, attitudes, abilities & lifestyles to conclude that you will have the same experience as him.

No matter how much in common you both may have, at the end of the day, this thing will be going on your head, not his.
You could be identical twins, but, for example, if your skin type is slightly different, your experience will be bear no comparison.

In your opinion poll one of your possible answers to 'is it undetectable' is: "Yes, but with hard work"
Whats 'hard work'?
It can sometimes be a pain, it can sometimes be inconvenient or time consuming.
Is that 'hard work'?
If you're really pleased with the results, you may consider it an effort, but a rewarding one.

Or you may be one of these people who slap a bit of tape on, stick it on their heads & are ready to go, because for you its more about getting on with your life and not letting your hair control you.

You won't really know until you try.
Gathering information to help you on your way is a good thing.
But you'll have to differentiate between opinion & facts when you get replies.

Mostly you'll get opinions based on people's personal experiences and mostly pertinent to them only.
The facts, for you, will be found in your own experiences.

Most decent suppliers are selling basically the same products (albeit at varying prices) so really it comes down to the wearer, not necessarily the piece.
Its HOW you wear it and the choices you make when ordering that determines detectability.

In my opinion your research is misguided and you're not really asking the right questions.

What if the answer to your question "Can pieces be undetectable?" comes back as a resounding "YES".
Does that mean you can go off and get one attached and yours will be undetectable too?
Do you believe that "YES" answer automatically applies to all pieces & all wearers?

Your question should have been, "What makes a piece undetectable?"
Then you would have learned about graduated hairlines, proper placement, different attachment methods & tips.
This is information that could really help you and is freely given on this forum.

I think its rather telling that so far no one has actually participated in your poll, but instead have responded with real information.