I've never heard anything that sounds as natural as AIR engaged on the HG-2, also night and day when comparing it to the plug-in. I feel like it just opens up the top of a mix ever so gracefully, but I definitely could see how when mastering most mixes it might feel a bit too much.
I think why it works so well for me is because most anything I work on nowadays I'm part of the process from the very beginning, and i'm able to not over do anything in mixing that might hinder my ability to really push my mastering chain in a way an overdone mix wouldn't allow, and the HG-2's AIR engaged(stock) is absolutely stunning, nothing like it.
Both tracks below have it engaged(as well as tons of other things). If you listen to Sammy Bel Mar's voice on Cold Start and how natural the highs sound, as well as the rest of the vocals and everything else in both tracks, it doesn't sound like too much to me, but that's my opinion of course, we all hear things differently.
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Latest release
Crispy - STELF made | Spotify
Previous release
Cold Start - STELF made, Sammy Bel Mar | Spotify