168cm tall? Oh, in that case the Ive would work for you. No problem regarding height there.
The Birdy Air has a fixed length handlepost I think. Seems quite short too.
I'm quite certain that, paint jobs aside, the P10 and X11 have the same frame which has been improved/upgraded for strength. I've never read or heard of anyone having problems with this frame.
If I were to buy again, I would buy a P10 instead of an X11 I think, as the P10 is in a nice price vs performance sweet spot. Yes, the X11 has nicer components, but its kindy pricey really (thought I did find a good deal) I'm sure I would have been perfectly happy with the very good components on the P10. And the P10 still has excellent hydraulic disk brakes. After experiencing the hydraulic disk brakes of the X11, I'm never going back to using caliper or V-brakes. The performance difference is night and day.