The recruiter from the first company to give me an offer, told me it is pretty much non negotiable, "we have a little wiggle room but don't expect much, it's an amazing offer". It was higher than my then salary, but not by a huge margin.
Then company B got back to me with a significantly higher offer both in terms of RSUs (x2) and base salary.
Well, turned out the non negotiable offer was very negotiable after all, and company A quickly upped their offer above company B's. At this stage it just became a back and forth bidding war, that ended after a couple of weeks with two almost identical offers, 50% higher than the initial TC.