You’ll need a reverse proxy if you have two containers. You’ll want to do a two container install so that you have only one postgres running. You’ll need at least 2gb to do it, though 4 might be better, so if you hope this will save money over a single 1gb vm, you’re better off just using two small vms.
It’s an advanced setup, so if you’re not already familiar with a two container install, it’s going to be some work.
The multisite topic has some hints about setting up multiple databases.