Defining which options to install can be done at creation time as long as the database doesn't come from a seed database. If you created a database using the DBCA customized creation option then you may want to install other options later.
Don't install more options than required; either way you can go back to the DBCA edit Option to add them at a later time.
Database Edition only works to add database components, not to remove them, that is why if you come back later to try to disable components you will find that the already selected components are not eligible.
There are other components that may appear as not eligible too, such as Oracle Label Security(OLS) or the Sample Schemas. If these components are grayed out this means the component has not been installed. In the case of OLS this is included on the database disk, but it is not installed by default. In the case of the Sample Schemas, those are not available on the database disk, but can be found on the companion...