While anything is possible it seems unlikely that Opus is causing the delay, in that case. The option causes Opus to ignore all 3rd party context menus so it is presumably one of those menus which is causing the delay.
The Finding The Culprit section of this FAQ may help you track down which program's context menu is causing the problem:
[Crash, exit or high CPU when right-clicking certain files)
Basically, you turn off the "Hide Windows items" option that you just turned on, and also enable a debug setting, and Opus will then print a list of context menu extensions as each one is queried. With any luck one of the extensions will take much longer than the others (i.e. there will be a longer delay between it being listed and the next handler being listed) and that will point to the cause of the problem.