Mi mix user here, wondering how does the size feel?
Ajusted to it quickly?
Honestly depends on many things. I can adjust to just about anything.
As of now, I'm torn between the OnePlus 6T and the Mate 20 X. Size wise the 6T is so much easier to use, and with GCam development coming along, the pictures the 6T takes is simply amazing. I hate to say it but the Mate 20 X doesn't have great portrait modes. I've been testing both the Mate 20 X and the 6T extensively and while I was drawn to the Mate 20 X for its camera, size, battery life, etc. It looks like the camera is letting me down a bit for certain situations.
I could ramble on, but if you're genuinely only interested in size - you get used to it if your hands are of decent size. I've been told I have slightly above average hands and I can use it very well. While holding it with one hand, I can type and reach the "q" and "p" on the keyboard with a slight stretch.
My only gripe with the size being the actual software.. Huawei has poorly optimised the space available. On a 6.3" screen, I have 6 quick setting icons on the 6T. On a 7.2" screen, the Mate 20 X has 5. The icons look cartoonishly big.