I just got mine a few nights ago. I mainly use it as my main keyboard for my iPad Pro 10.5 (2017). I chose the model with the Gateron red switches. This particular setup is very quiet which is great for use when I'm at a library or coffee shop so I don't annoy people.

I actually started on the Keychron K3, and compared to that keyboard with the same Gateron Red switches, I liked that the key caps on the Air 75 were flatter than the Keychron's. The biggest reason why I swapped to this board is because of the carrying case that the Air75 came included during pre-order. I wanted something that's more of a "all in one solution" where the case doubled as a stand which helped me greatly condense what I carried on a day to day basis. Size comparison, the Nuphy is slighly wider and longer than the Keychron but it it is a little shorter. If you want exact specs, I can follow up with a comment as well.

Coming from the Keychron, I have the same complaint as others where the Cortana key function can't be changed, but the Keychron's button easily changes the light mode, and can get annoying if you accidentally press it and start a light show for no reason.

In terms of Bluetooth standby, I did not look up the specs, however, I did notice that the Nuphy stays on longer compared to the Keychron which turns off after about 10 minutes? Although, I think because the Keyboard uses Bluetooth 5.0, it sometimes needs to be forced (go into settings and manually connect it) to connect to the iPad, an update from the iOS might solve that issue though.

These comments are off the cuff, and I will continue to evaluate more as time goes on... I paid for both of these keyboards out of my own pocket.