I transferred my vampire celeb to a fresh save. Still noticed some lag, but no freezes. However, I noticed her vampire perks seemed to be bugged. She was unable to gain any more power points, and when I reset her points using the draught of reconfiguration, the power selection screen seemed to be bugged as well.
Today I did another full reset. Downloaded my sim from the gallery and started over in San Myshuno. Brand new save. No freezing so far, but I do have a bit of stuttering. Oddly enough, I even noticed some in CAS. Can't remember that ever happening before.
Is it possible the old save just got corrupted somehow?