So:

I get that if I leave my startup today I have 90 days to exercise my options.

I get that I'll have to pay the agreed 'strike price'

But everything after that is unclear to me.

Would I be paying tax as if I'd made capital gains in the amount of the delta between the strike price and the stock's value today? Would the stock's value today be based on the company's valuation at the most recent round of funding?

If the company goes on to raise more VC funding, would I be liable in future years for the 'capital gains' on this stock?

If the company went on to fail, would I be entitled to tax breaks for loss of stock?

etc.

I'd love to see a clear explanation of all this stuff from someone who's been through it or just knows it. Thanks!