I made a sim just for this question, so here goes :
The time sim take to enter a car when going to work, well, of course it depends on how big is your house, how big is your front lawn, how many stories is your home. so i can't test that, it will be useless. right?
And for the Mac and Cheese test, all test done with fixed variable :
-The distance between fridge, stove and food processor are just 2 tiles maximum.
-All the sim are without Challenge reward (cook faster)
-I stopped the clock when the sim take the pan and it change shape to a bowl.
trivial : when i did this test, the stove actually burst into flame and i have to wait for the fireman to extinguish it.
A sim with 10 cooking skill, No related trait, without food processor, with most expensive stove : 45 Minutes
A sim with 10 cooking skill, No related trait, with food processor, with most expensive stove : 36 Minutes
A sim with zero cooking skill, No related trait, without food processor, with most expensive stove : 1 Hour 3 Minutes
A sim with zero cooking skill, No related trait, with food processor, with most expensive stove : 50 Minutes
A sim with zero cooking skill, No related trait, without food processor, with cheapest stove : 1 Hour 6 Minutes
A sim with zero cooking skill, No related trait, with food processor, with cheapest stove : 59 Minutes
A sim with zero cooking skill, Natural Cook Trait, without food processor, with cheapest stove : 1 Hour 14 Minutes
A sim with zero cooking skill, Natural Cook Trait, With food processor, with cheapest stove : 50 Minutes
not all variable are tested but i hope this give the figures you need. i think sim with natural cook with 10 cooking skill will be faster. i hope i can help you more.