Hi,
you can grade in rec709. should be fine.
probably you dont need to convert to XYZ in final.
most of the time DPX rec709 sequence is fine to make film out and DCPs.
but this is with you and the final lab.
resolve outputs 2k and 4k. in mov files or dpx, or whatever…
you can have your 4k material in a full HD sequence, and grade it,
in the end you can put your sequence in 2k
I graded some movies in a rec709 hd monitor and its fine.
remember that for DCP, the gamma should be 2.6 instead 2.2 of regular rec709.
and it makes a lot of diference in dark areas.
well, in cinetal I did that way…
have fun!