Also, I can personally testify how important negotiating the offer is. I routinely (every ~2y) interview to discover my market value and, from a position of power (e.g. "Well I'm happily employed at the moment so the incentive has to be good" or "I have a higher offer"), is very easy to negotiate additional stocks. I've been able to improve the offer by a good $100k yearly RSUs (!!) just by negotiating with HR. It also helps that I kind of like the process (I'm that weird person who gets thrilled by buying a new car and making a car salesman lose his patience by constantly asking a better offer and absolutely be ready to leave if it doesn't happen)
How do you respond when they insist on knowing your comp details?
The only case where it can be beneficial to disclose something about your compensation is if you have deferred compensation (e.g. stock options) that you want your potential new employer to somehow consider in the offer. In that case, sharing a copy of the grant is the easiest thing to do, and doesn't hurt much
Do you postpone comp-talk until an offer is on the table? Or is it safe to assume that large companies generally have an extremely elastic range?
Do you think it's a good idea say something like "If you can offer $OBVIOUSLY_EXTREMELY_HIGH, i will immediately accept. For lesser offers, i will evaluate them on a case by case basis."
Did you ever read Chaos Monkey? (https://www.amazon.com/Chaos-Monkeys-Obscene-Fortune-Failure...)
The author was a founder of a very little startup (3-men shop) and after 6 months tried to approach Facebook to be acquired, and Facebook told him: we don't want your technology, but since you have proven to be capable of building something exceptional, we want you to join (and you can throw away your product), and we'll offer you $2-3M (don't recall the exact number) in RSUs with a 4y vesting schedule, which he clearly accepted.
Now, those "acqui-hires" happen all the time among those big companies. Since the acquiring company is clearly not interested in the product but just in the talent, how is that different than getting in the door as a really solid individual contributor with terrific experience in getting stuff done (of course, your resume and interview skills need to reflect that, and also, probably even more importantly, your negotiation skills). You can choose to not believe me, but the answer is that there is no difference at all.
If you live in the valley, I can't believe you don't have an acquaintance who followed exactly the path of being individually "acqui-hired" as a talented individual contributor (but not being part of a real acquisition, mind you), which is exactly what happened to my two friends described above (no direct reports, purely technical gig). They are very very good in their fields and managed to sell themselves very well to the right teams inside those big companies.