We have remote teams in different countries. What is the best way to setup repository server?

There're two choices:

1. Setup a central RS with public IP so that all clients can connect to.

2. Setup one RS in each country. Local clients will connect to local RS. All RS will synchronize the data using replication feature of TestArchitect. From network perspective, you have to make sure all the RS are in the same network so that it can talk to each other. So you probably need to use VPN or something similar.