Martin,
JFBConnect is already responsive. Our SCLogin module and social widget features are ready for responsive templates and, should you have issues there, we'll gladly help.
Regarding EasySocial, we'll have full support for integration with it later this year. There will be support for Facebook, Google+ and Twitter authentication along with a lot more configuration for options like customizable profile import from each of those networks. We'll also have Open Graph tags and Actions support to describe your pages and automatically post that content back to Facebook.
For EasyDiscuss and EasyBlog we don't currently import profile data into those, but EasySocial (I believe) can take your profile and push it into those extensions, so that should be a problem.
We do have Open Graph Actions support for EasyBlog.
Finally, we support profile import, Open Graph tags/Actions and social buttons for K2.
I hope that helps explain, but if you have specific questions, just let me know.
Thanks,
Alex