I love [name]Gwen[/name] names!
[name]Gwendolyn[/name] and [name]Gwendolen[/name] are pronounced the same. [name]Winnie[/name] is absolutely a nn for [name]Gwendolyn[/name]/len. I’m not sure I understand your question about [name]Gwyneth[/name] - I’ve always heard the [name]Gwyn[/name] part pronounced like [name]Gwen[/name].
I love [name]Gwendolyn[/name]. I like both spellings though. Personally I pronounce them both the same. len and lyn are basically the same thing to me. I think [name]Gwendolyn[/name] just looks softer for some reason. I say [name]Gwyneth[/name] [name]GWIN[/name]-eth.