Whenever you have the option to choose between “optimal” and “optimum,” opt to use the first option as an adjective and the second option as a noun.
Option 1 Example: “What do you think would be the optimal temperature?”
(the adjective “optimal” modifies the noun “temperature.”
Option 2 Example: “I think 72°F would be the optimum.”
(the noun “optimum” has the article “the” in front of it)
The same rule applies to “minimal” and “minimum.”
I am optimistic that you will optimize your usage of these words at the very minimum, thus the need for correction will be minimal.