Application Extensions vs Visual Applications?

Summary:

Are applications extensions and visual applications mutually exclusive? Can you only have one or the other in your VBCS environment?

Content (required):

Just as the summary says, i'm only looking to find out if Visual Builder can have only Application Extensions OR Visual Applications, or if it can both?

Also, does this extend to OIC CI/CD functionality? For example, if I have the environment set to up to modify pages in the Fusion HCM application and set up the CI/CD pipeline for that, can I also have my OIC instance in a different pipeline?

Version (include the version you are using, if applicable):