FSAs do depend on you kinda predicting or hedging bets against your own health since they only last the year. You can also use them to buy certain health/exercise equipment though.

HSAs can often be invested (in stock market) thus act like an IRA with extra tax avoidance if you manage not to use it for long enough. It’s counter to the stated purpose but it’s basically better to not withdraw or reimburse from it unless you need to.

Deductibles are Deductibles. How much you have to pay before insurance “kicks in”. There are per visit deductibles and yearly deductibles which are as they sound. HSAs are only available to plans with high deductibles. FSAs are available to plans that aren’t just high deductible.