Folder content detection is off by default in Opus 10 (on a clean install) so upgrading from Opus 9 to Opus 10 shouldn't turn it on. As far as I can remember, it would be left as-is. There could be something more subtle at work, though, like the detection was always on but all the actual Content Type formats had been deleted before (so there was nothing to detect before) and the upgrade then added them back.
Folder Formats should be preserved on an upgrade, except possibly formats for virtual system folders, but the way the main ones (Computer and Desktop) are displayed is completely different in Opus 10 anyway, so those two would have to be reset. Normal folder formats should be preserved, though, unless something went wrong.
Since you've got a backup of your Opus 9 config, if you want to check if the performance issues you're seeing are config-related, you could do an uninstall (which will wipe your config) and then reinstall Opus 10, and see if you get the same issues with a completely default config.
If the issues are still there with the default config then it's probably something external to Opus (shell extensions, drivers, etc. as suggested in the other thread), since if there was a problem caused by the defaults then we'd definitely know about it by now (they're over a year old and we'd have had hundreds of complaints).
On the other hand, if the issues are gone with the default config, but come back when you import your Opus 9 config backup, then that points to something in the config as the trigger. If that happens you could send me your config backup, if you want, and I'll see if anything stands out as a likely cause.