How would I achieve hollow cheeks? Would I need lipo, Kybella, or fillers?

Kybella has serious side effects including temporary and permanent nerve damage. For this reason, injection of this inflammatory medication is limited to the submental area.  Kybella is a bit disappointing as a fat sculpting product even if the advertisements are amusing. Removal of buccal fat does hollow the lower cheek.  Your model probably has also had her back teeth removed and may have a chin implant. She is likely 3 percent body fat.  In fact, someone desperately needs to feed this person a nice meal. Honestly this is not a health look and I caution you in trying to achieve it.  Under eye filler could help you but you need to see someone who understands something about the rheology of these fillers.  Runny fillers like Voluma and Juvederm tend to drift after placement.  Avoid permanent or semi-permanent fillers that can't be removed.  That includes products like grafted fat, sculptra, and Bellafill.  Bellafill is the new name for Artefil which leaves plastic beads in the body that scar in place.  That is bad if there is a problem with the product after placement.  Stay with products that can be removed without surgery no matter what you are promised by your potential injector. Don't harm yourself in an effort to look your best.

Buccal fat excision is an appropriate surgical procedure for patients that of overly full and wide cheek areas. In common terms, it is good for patients who have chipmunk cheeks. In reviewing your pictures, is difficult to tell if you're a good candidate because your cheek area is slightly full but not overly full. Facial liposuction can be used to slim the face. You are a patient that would need and in person consultation for a complete evaluation and explanation of the positives and negatives of each procedure in your situation.
I hope this helps.

Typically, fillers do a nice job of recontouring the face. Cheekbones can be enhanced which will create a more hollowed appearance. I would be cautious about removing fat from your cheeks since loss of fat from the face contributes to the aging process when you are older. Please consult a board certified dermatologist or plastic surgeon experienced in facial aesthetics. Best wishes.