I don't know if there are any duplicate detection tools in LR/Cloudy so won't comment on that part of your last post. However, I will comment on the other part. However if you've followed the advice in this thread, and you no longer want some of the images in the Cloud since they are known to LR/Classic, just remove them from all sync'ed collections (including the "All synced Photos" collection) and they'll be removed from the cloud.
In your first email you said you were replacing the old laptop with a new one. Assuming it's a windows/10 or MacOS machine it should be able to run LR/Classic just fine. So, I'm not sure why your are interested in burning your bridges so to speak by ditching your LR Classic Catalog? Especially before you've had a chance to really see if LR/Cloudy is capable of what you need. If you've done anything in LR/Classic beyond image editing basics I suggest that you'll be disappointed with what you can (or in this case can't) do in LR./Cloudy.
A second point is that up till now, we've been advising you on how to use LR/Cloudy along with LR/Classic and not have to pay for more cloud storage. But now you're talking about getting rid of LR/Classic altogether which makes all the suggestions we've provided so far not applicable to your newly divulged plan. For starters, what we've suggested relies on you having your original images on your laptop and known to LR/Classic. If you ditch LR/Classic you may or may not have your original "out of camera" image files (depending on if you copy them to the new laptop or not) and they may or may not have XMP sidecar files to provide the look for whatever you've done with those images in LR. What you'd have in LR/Cloudy are reduced size DNG "Smart Previews" which - while perfectly fine for editing purposes - are not your full resolution images.
I strongly suggest that you get your new laptop, Copy the entire folder containing your current LR/Classic catalog to the new computer. Then copy all your image folders to an external hard drive or copy them to the new computer's internal drive as well. If you ever get to the point where you are sure the LR/Cloudy has all the features you need and is giving you the results you desire, you and then decide to depricate LR/Classic. You would do that by "migrating" the LR/Classic catalog to the Cloud (where you were when you first started this thread) and be ready to pay lots more $$$$ for additional cloud storage when you run out.
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