For fishless cycling, a bottle of ammonia is much more controllable than fish food. With food you can never be sure how many bacteria have grown so you would need to stock slowly as for fish-in cycling. When you use ammonia, and follow the method on here
https://www.fishforums.net/threads/cycling-your-new-fresh-water-tank-read-this-first.421488/ you know at that at the end of the cycle you have enough bacteria for a sensibly stocked tank of fish.
During fishless cycling, nitrite needs to stay below 15 ppm (though our test kits cannot measure that high, which is why the method in the link was written, to stop it reaching that level) and nitrate can be as high as it likes. Once the cycle has completed, a huge water change is done to remove all the nitrate made during cycling. It is only after the cycle has finished that ammonia and nitrite should be zero and nitrate below 20 ppm - though of course cycling with fish is different as those levels need to be maintained during a fish-in cycle as well.
pH does not have to be 7.4 to 7.8. Soft water fish are happier in a pH below 7.0. It is only hard water fish which need a pH above 7.0.