But, in the first place, why did you choose to NOINDEX, FOLLOW those product pages?

If you have a preferred product page among those different variants seen as duplicate why don't you just use canonical to point there?

What do you think is the benefit of noindexing? Theoretically leaving them there with the duplicate content and a canonical you are wasting some google bot crawling budget, but unless you need google to crawl your pages with a high frequency (because your content is frequently updated) I wouldn't care much.

Personally I see de-indexing as the last resort.

In addition to what have already been said, I would consider adding rich snippets such as schema.org/author

http://moz.com/blog/a-visual-guide-to-rich-snippets

After googling about it and thinking better I choose not too. I think you are absolutely right, too inconsistent.

Is it legit to show different content to http request having different referrer?

case a: user view one page of the site with plenty of information about one brand, and click on a link on that page to see a product detail page of that brand, here I don't want to repeat information about the brand itself

case b: a user view directly the product detail page clicking on a SERP result, in this case I would like to show him few paragraph about the brand

Is it bad? Anyone have experience in doing it?

My main concern is google crawler. Should not be considered cloaking because I am not differentiating on user-agent bot-no-bot.

But when google is crawling the site which referrer will use? I have no idea, does anyone know?

When going from one link to another on the website, is google crawler leaving the referrer empty?