The goal of inventory control is to be sure that optimum levels of inventories are available, that there are minimal stockouts (i.e., running out of stock),

Optimum is correct.

There is a streaming application that allows one to control their television from a mobile phone by Cablevision. The application is called Optimum application.

In her search for optimum health and the ability to control how one feels by what one eats, she became a professional cook, lecturer

The plural for optimum is optima.