My two cents but not about the Billie.
There is a lot of good stuff out there and the price points seem to be dropping for better stuff. However, the other factor with the reviewers is that they are getting products to review from some manufactures. So you will see about 4 or 5 reviews on the same product like the Billie because the reviewers are being supplied with the product.
What you have to remember is that there are numerous other manufacturers who are smaller and even one man shows who either do not or can't supply this endless supply of YouTube reviewers with sample products to review.
So that's why I think it is a good idea to come to forums like this to get ideas from experienced users who have a wealth of experience and know about various products that maybe you've never considered or heard of.
The Billie is the first or only hybrid amp -- it is just the one that is being pushed out by all the YouTube reviewers. That doesn't mean it isn't good but there are probably others which have done the same or similar thing that don't get the "press."