I'm not sure what list of websocket addresses you're referring to; you linked the same page twice. The answer to your first question is that there's no need for a lookup. The DNS names for Genesys Cloud are static and do not change. You can find information about Genesys Cloud domains, IP addresses, and related topics here: About ports and services for your firewall - Genesys Cloud Resource Center
Hi @SzabolcsGergye thanks for raising this. We will update Web Messaging & WebSocket documentation to include US-East 2 (Ohio): we are finalizing the necessary testing for some scenarios.