Building on the basics from How to filter items by location or sub-folder, you can tell Opus not to look inside sub-folders whose locations have too many \ characters in them.
The Location clause tests the full path to the parent of an item.
C:\one\two\three\four\five has location C:\one\two\three\four which matches **** and means that the five folder (and any below it) will not be entered when searching.
Remember that Location is always an absolute path. If you want to limit the depth relative to where your search starts from then you'll have to adjust the wildcard string.