Google recruiters have a range for each component. Your job is to move them toward the top.
Use competing offers. A Meta or Amazon offer at the same level gives you concrete negotiating power. "Meta offered TC of K at E4. Can Google match or beat this at L4?"
Negotiate components separately. If base is at the cap, push on equity or signing bonus. "I understand base is capped. Can we increase the RSU grant by K?"
Never reveal your current salary. In many states this is illegal to ask. Focus on the market rate for the role.