Keeping the frame rate above 60fps is paramount, and ensuring the frame rate stays stable is key. Without this, you risk motion sickness. The human vestibular system is a fickle beast. This means discussing with your development team what the aesthetic limits of your world are. Lower fidelity and higher stability is better than higher fidelity and lower stability. PSVR, being lower resolution but running at 120fps, is a good example of this at a hardware level.