Our software do support Duet on iPad Pro, it runs pretty smoothly in 60 fps. There is a little latency due to duet connection, but not really an issue.
Ipad was connected using usb C cable to the macbook pro, FYI
Also, if the iPad is connected through wifi to your computer, you may encounter some display lags depending your wifi generation and bandwidth.
We have not tested using 'non pro' iPad, FYI.