Negotiable: RSU grant amount, signing bonus, start date, remote work (team-dependent), relocation package.
Partially negotiable: Base salary (has a band per level, usually \10$20$K flexibility).
Not negotiable: Level (determined by interview performance and hiring committee), performance bonus target (set by level), vesting schedule ( years, -year cliff).
If you think you should be leveled higher, this fight happens before the offer. Once the offer is made, level is locked.