I'm fascinated by the fact that we can set the fee. Suppose I set it to the minimum (or zero...?) is the transaction guarenteed to go through (with the delay)? Thanks.
Some web wallets doesn't allaw their customers to customize fees.
a transaction with zero fee will not be relayed. The minimum is 1 sat/b (1 sat/vB for segwit transactions).
Transaction confirmation time depends on how much fees you pay though. The higher the fees are, the faster your transaction get confirmed.