Hello Josep,
Thank you for your feedback.
We do not have a plan for unlimited websites or a plan for 100+ websites.
The difference is that the plugin you’re mentioning does not have a free version, but only paid version.
So depending on a website you may not need some pro features. and in the case of the other plugin if you only need Page Caching or Minify you have to pay for it one way or the other, which is not the case with W3 Total Cache.
IF you have any specific number of websites you wish to activate the Pro version on, please reach out to us directly via email.
Thanks!