Hexus has released a review of the ASus RTX 3070 Noctua Edition. No surprise, the 4.3 slot card is the quietest and coolest air-cooled GPU they've tested. Additionally, the card actually runs in a passive mode most of the time, and the back plate is more brown then previously expected.
If you have an SFF case with the space for it, and are dead set on the quietest GPU, it looks like Asus and Noctua made your card...if you can find it.
Be sure to check out the Hexus review by following this LINK.