Would threads or buccal fat removal be better for my once tight jawline?

I believe you asked a related question (realself.com/question/sydney-au-treatment-sagging-face-skin-needling-rf-tightening).
The principles are similar: - Address the sagging; - Slow-down the rate-of-ageing.
My advice is to avoid filler and to avoid HIFU (e.g. Ultherapy) to the area.
De-bulking the fat, tightening the skin, holding the skin in that position, and improving mid-face projection, would be my advice - but, of course, I haven't examined you and you haven't uploaded any photos.