The only info relevant to CX is that BRU check in desk closes 75 minutes before departure https://www.cathaypacific.com/cx/en_...s-airport.html , and as a general rule you have to be at the CX gate 20 minutes before.

LH as a rule will not check in separate tickets (if that is your case), but you can confirm in https://www.flyertalk.com/forum/luft...iles-more-495/

BRU immigration, fast track (or lack thereof) will be answered in https://www.flyertalk.com/forum/europe-477/ (asking for this thread to be moved)

(but PS - this answers most of what you have to know about BRU for non-LH non-Schengen airlines https://www.reddit.com/r/BritishAirways/s/2Nq02uzUz7 . Read CX as getting the same treatment as BA)