read only replica and cross-region standby database for SQL Server 2014 EE

Hi, Gurus, 

I am new to SQL Server and looking for suggestions. 

We have a MSSQL database running SQL Server 2014 EE. Planning to create a read only replica within same data center and a standby database  in remote region. 

Have been searching options from google and found this forum. 

For read only replica, we just want to offload the read operations to a different server . In this case,  which option is  better ,  transaction replication or always on availability groups? 

For standby in remote DC, its is mainly for HA/DR purpose. Will mirroring be a good choice? 

Thank you