12. If I delete duplicate presets from the User Presets area in Lightroom, will that only delete the presets from that area or will it delete them from somewhere else, too?

The DVLOP installer used for Visual Flow Presets is universal and it installs versions for all of Adobe’s fragmented eco-system. The files you see nested in the Visual Flow folders are for the latest versions of Lightroom and ACR. The files that you see in the main settings folder are NOT duplicates. They are the correct files for older legacy ACR installs. Adobe can’t see them unless they are in the parent folder. Adobe automatically organizes those into the lightroom ‘User Presets’ folder. You can feel free to delete those without any issues if you choose, but they are not duplicates and they won’t do any harm.