First of all - not an expert, so take it for whatever it is.
From what I know for bookkeeping purposes during the season, at the beginning of the fiscal year the contracts that include incentives include all incentives that are deemed likely, and exclude all incentives that are deemed not likely. if I'm not mistaken "likely" incentive is one that the player did cover the requirements for in the previous season and unlikely are the ones that he did not. For example(not real example, just for illustration purposes), lets say Rudy has incentives in his contract for playing 50+ games. If he did play 50 last year, for bookkeeping purposes they will include that incentive in the salary cap during the season. Lets say he has an incentive for being DPOY. This incentive will be deemed unlikely and won't be included in the calculations during the season because he didn't become DPOY last year. This all is for bookkeeping, for apron and hard cap numbers, etc. Ultimately whether we pay tax or not is decided at the end of the year when we will know which incentives exactly the players hit, which ones they didn't. Note - it's possible that our salary cap drops(if players don't hit some likely incentives), BUT it's also possible it jumps up if they hit some unlikely incentives.
On the second one - I don't know. I would assume yes, BUT, it also is probably very reliant on the exact numbers. I'm still seeing discrepancy in the numbers being calculated by several different outlets so I don't know which one is real. Some say we are 1M over, others 1.7M... some have it at 1.9M.