Just assume startup equity will be worthless (which it almost always is).

whatever they value their options at in negotiations, multiply that by 0.1-0.25 to get the real value in the best outcome for a late stage startup (series B-C+) as a common employee

Without information about the cap table and liquidation preferences, assume the cash you are getting is the only compensation you will receive. To make it easier, if you are not using your lawyer during negotiations, I would assume the cash portion is the only compensation.