Recalculation Speed vs. Clarity with Nested IFs

I have a column of formulas with a several nested IF statements on a table with thousands of records. The data I'm processing is pretty consistent on the proportion of records that will branch into each of the IF true/false paths. The time Excel spends recalculating cells in this table is of paramount importance to the project.

For clarity's sake, and since formulas with boatloads of nested IF's can get so hard to follow and maintain, I'm considering pre-calculating the true/false conditions that drive each of the branches into separate table columns. The (potential?) drawback I fear of pre-calculating IF conditions on separate columns is that I'm forcing Excel to recalculate these criteria on every row of my table.

My question is on Excel's evaluation of nested IF statements: on a given cell with nested IF's, does Excel calculate every possible IF branch in the formula? Or does Excel only calculate the criteria needed to get the result, skipping the more infrequent conditional branches?

Thanks!