I think generally speaking, people tend to post what's expected on group rides from what I've seen. Pace-wise, I haven't ever been on a group ride organized on this forum that didn't stop and wait at intersections for slower riders, and I was one of those slower riders so I took advantage of this perk, quite often after my lowside 2 years ago.
As for getting more comfortable with cornering - track day. You don't have to be a junkie with a track bike, full leather power ranger suit and thousands of dollars to burn in order to run a track day or two. The way track days are organized, they are a school in the less experienced groups. An "instructor" or control rider will be paired with you and will give you feedback on what you should/can be working on to improve. They will show you the lines of the course and are a tremendous wealth of knowledge. I encourage everyone I talk to that hasn't done a track day and expresses an interest in becoming a better rider to go to the track at least once. It's set up in such a way that, like a ski/snowboard lesson, there's the bunny hill where you can start out (novice group) and it scales all the way up to double black diamond back-country deep powder runs (advanced/open race practice).