As a test, if you turn on Preferences / Folders / Folder Display / Show generic icons for... and set it to ...all folders, does the slow-down still happen?
As a second thing, it looks like a column like Description is turned on (or you're in thumbnails or tiles mode, perhaps) which is causing Opus to inspect all the file contents (since it shows information like image width/height that requires opening files to calculate). That's probably not desirable in a cloud storage folder, although I'm not sure if it's involved in the main issue or just making things slightly slower.
No, just name, size, date, as per my screenshot. Are you basing that on the dumps I emailed?
No, in detail mode
Another small update: I did notice that the 1k sub-folder folder is loading after a short while now, whereas the 11k sub-folder folder is loading after maybe five or ten minutes, not sure exactly how long, I wasn't watching it.. This is before the preferences change you suggested.
Again, there's no such delay in Total Commander and Explorer.
@Jon Yes! That makes it load instantly. What does this mean?
Display localized folder names : Vista introduced the concept of localized folder names. In Windows XP, the C:\Program Files directory (for example) is physically renamed in other languages - e.g. on French systems the folder is C:\Programmes . In Vista and above, the folder is always called C:\Program Files , but its name is translated when it's displayed in the user interface. With this option on Opus will display the localized name for such folders instead of the real name in the filesystem.
So just keep it turned off I guess, if you're using Google Drive File Stream?
To test the alternative methods, please turn back on the Display localized folder names option.
Also please verify that you still get the slow down in the default state before proceeding.
Add a DWORD value to the registry under HKEY_CURRENT_USER\Software\GPSoftware\Directory Opus called LocalizedNameTest. Set the value to 1 and see if that affects the speed of reading the Google Drive folder.
Then change the registry value to 2 and repeat the test.