If you can see which process or processes are using a lot of resources during the problem, or even better generate a dump file (Manually Generated Dumps section) for some of the affected processes, we might be able to shed some light on where the issue is coming from and confirm whether it is Opus or something else.
Opus does not have any real interaction with tools like Lightroom or the way other programs paint their windows, and we have not had any similar reports like this, so it seems very odd. It can't be just the combination of Opus and Lightroom, as we would have a lot of reports for such a major issue.
One thing worth trying is to set Preferences / Miscellaneous / Advanced: no_external_change_notify to True and see if that makes a difference. If it does, something may be flooding the Windows change notification queue with an enormous number of events, which could cause Opus to use a lot of resources (in addition to the resources used by whatever is causing the flood). If that reduces or prevents the problem, there are some other things we can suggest to track down the cause of it, but they're only worth detailing if they turn out to be relevant.