Both the Solemn Painting and the Mystic Statue in your opening post looks like they are genuine.
I have two AC:NL screenshots from 2017 when Redd offered three authentic art pieces in one of my towns. This was in a town with perfect town status, high feng shui points, and was enjoying items luck day (according to the Lovely Phone).
6 Jan 17:
Beautiful Statue: Authentic
Proper Painting: Authentic
Flowery Painting: Authentic
Whatever it was painting: Fake
18 Aug 17
Scenic Painting: Authentic
Worthy Painting: Authentic
Flowery Painting: Authentic
Beautiful Statue: Fake
Here's a link that may help identifying Redd's art:
https://www.jvgs.net/guides/acnl/crazy-redd.shtml