I would recommend setting the system res to HD, and then flip it to 2K when you are ready to render.
The main benefit is almost 50% more performance during the grade, although you do incur the cost of resizing the image to HD during the grade.
Resolve has window tracking which tracks windows, etc when you switch resolutions, or apply Input PTZR.
The alternative is to monitor as a HD crop, either at system resolution, or as output format.
Regards,
Rohit