The LinkedIn popup won't work immediately with JLinked. It's a whole different authentication flow that we'd need to implement.. and it requires SSL. With v2.0, hopefully we'll support either it, or some sort of modal popup for the current window. Still need a lot of testing and development to see what happens though.
As for JFBConnect, the linking process is simple. There's a few ways to do it:
1) There's a "Automatically link user's by email" option where, if a user logs in through Facebook using an email address already on your Joomla site, their accounts will auto-link. No forms required.
2) On the JLinked Login / Register page, a "Login With Facebook" button will appear on the Login portion to let user's login that way and connect their accounts.
3) If a user is already logged in, the SCLogin module can show the Login With FB button to let user's manually link their accounts.
Once linked, the user can login with Joomla, FB, or LinkedIn and get into the site easily.
Finally, for the JomSocial email field, we can help you add support for that field if you want it to show up in the mapping area. Shouldn't be difficult. However, JomSocial extends the standard Joomla user profile, so you shouldn't really need to store the email address separately in a new field unless you expect those 2 to be different. Hope that makes sense, but if not, just let me know.
Hope that helps!
Alex
V 1.3?
