Have played Alpha this month. Caviar is on my test list too. Will be able to compare them in a few weeks. To me Alpha feels as comfortable as YPTP, but i consider it a superior version because of more spin potential. So there is that. I'm also curious how caviar compares.
I think Alpha is significantly softer than Hyper G Soft. Hyper G Soft is about the same soft as Toroline Snapper, which is the softest poly in the Toroline line. And Snapper is significantly softer than Caviar.