@sam > A couple of things...
1) Provided you have added the BPM as an option for the sort column through rekordbox (click on the device name at the left, then click SORT, click BPM and ensure it's on the available side), then when you are browsing through your exported songs or playlists you can press the MENU button to change the sorting on the right column.
2) When you have two CDJs linked via ethernet, you will be able to see the traffic-light option (CDJ-2000NXS or NXS2 only), otherwise you would have to manually identify the key on one deck to find compatible tracks on the other(s).