Is it really free or will I have to put up with annoying pop ups unless I choose to pay for the "non-pop-ups version"?
The software is free, but you will be nagged with pop ups embedded in the pages you visit. The full version of the software doesn't have the pop ups and information embedded on the pages. If you don't want to use Hotspot Shield, then I recommend picking Tor Browser. It's a free solution with increased anonymity.
Download Tor Browser: https://www.torproject.org/projects/torbrowser.html.en