Windjammer

They can be complements and substitutes according to the book.

A manager with high explicit incentives is willing to have high implicit incentives, i.e. they are going to get fired quickly if they underperform their index.

A manager could have high implicit incentives and low explicit incentives as well. This would take into account that the implicit incentive of firing was high enough to pay someone less money.

Another case is low and low. Low paying job but low chance of being fired and easy management.