I'm curious, let's say someone wants to make clean install of windows, which method is cleaner? I tried reset PC briefly, it worked fairly well but I didn't really test it thoroughly...Will Reset PC preserve for example installed features, like WMC Add On, .NET Framework; and activation; or anything else?
Reset is Reset, it's a clean wipe. It will use a refresh image if available. Not sure if it will keep your activation, but it won't keep WMC or anything else you installed.
A clean install is the cleanest method, the refresh and reset methods are just there for ease of use for a 'typical' user. I believe reset means you will lose all installed features, activation etc, but it will still leave other stuff on the drive.
Refresh removes installed apps but leaves behind user data /files Reset reinstalls the entire OS and wipes everything