Is there any custom roms which supports proximity wake for ambient display ?
Yes in h2os ,since I have used that custom ROM only I don't know about other but yes ambient display option is present in h2os and h2os camera functions an ui is also ...
The easiest way to root your one plus x is via king root.
Download and open the app click on root voilà you have got root access.
After that download flashify from play store an grant it root access.
Open flashify click on flash new recovery imag...