You can try implementing IORM and it is an Exadata Feature.
The answer to your question is yes, it is better to consolidate all databases inside one or two CDBs, with each current database migrated to one PDB.
But you need to plan the whole process very carefully, as you have an old Exadata machine (Hardware) and outdated O.S (Intel Solaris) and old database/grid software.
To migrate to Oracle 19c, you have to install both 19c grid infrastructure and database, which has certification requirements with the Exadata software.
I may recommend you to refer to Note:
Exadata Database Machine and Exadata Storage Server Supported Versions (Doc ID 888828.1)
for latest certification information.