Please note that I'm open for any other replication method that would allow better scalability. One of the best option would be to have Multi-master setup though I haven't seen any documentation around the support for such capability by Postgres.
Postgresql doesn't support multi-master in the core project but there are options available. Have you come across BiDirectional Replication (BDR) yet? https://2ndquadrant.com/en/resources/bdr/