I tried the SQLite <> PostgreSQL on/offline set up. From my experience I suggest strongly to think about:
- How large is the data(base) to sync between off- and online (1 or n tables, just insert or also update (conflict-danger!)
- Data types you are using in each SQLite and PostgreSQL? Are they compatible?
- Do you have a tool available to make the "translation" from one DB language to the other easy?
I decided in the end to run everything on Postgres. At the same time it created new challenges: synchronization between masters. The conflict issue was solved by organizational responsibility outside the IT system.