We have OBIEE 188.8.131.52 and we already released the "Data Visualization" tool to the end-user.
Now we are considering the option to enable External Subject Area (XSA) Cache, but we don't know if the files that were previously uploaded by end-users will be moved to the new defined schema for XSA or not.
If it is not, we have an impact on turning this on as all the user should have to re-upload their files and re-create their DV projects.
OBIEE 12c: How To Configure The External Subject Area (XSA) Cache For Data Blending| Mashup And Performance (Doc ID 2087801.1)
Cache is created / written upon first usage. So if you modify the NQSConfig.ini and bounce OBIS, then the first running queries will fill the cache. Just like for "classic" cache.