We've seen noticeable performance improvements across all platforms. I would strongly suggest trying a fresh profile: Help > Troubleshooting > Reset Everything.
The performance gains have been the thing we've heard the most positive response on, so you're likely hitting some type of edge case. Happy to help dig if you're willing, but a profile reset would be a good first step.
Can you elaborate? Scrollbars haven't changed from 10 to 11.
This is tracked here: https://github.com/Komodo/KomodoEdit/issues/2694
Includes a workaround.
Very hard to say without seeing your use-case. Please consider logging a bug with some sample code.