I read in a blog that the elastic pool benefits were only for databases that have the same schema, is that true? Or do we get all the elastic pool benefits even with databases that doesn't have the same schema?
The databases do not need to have the same schema, there is no restriction on the schemas of databases that share a pool.
Elastic Pool is a way to share a set of resources (CPU, I/O, memory) among multiple databases in a server.
Here is a similar issue, you could refer to it for more details.