Hello Kmare,
I hope you are well and safe.
Follow below the answers.
1. Do we need to install email Router on CRM1 and CRM2 server ? Can I do it ?
Essentially Email Router is not load balance aware, you can install Email Router in any server, even to client machine. Basically Email Router will play a role of proxy/middleware between Dynamics 365 and email solution.
2. Do we need to apply CRM rollup on CRM1 and CRM2 server ?
Yes, it's recommended to apply update packages for all servers and components, such as server, Email Router, Outlook Client, and so on.
3. SQL is also in cluster. Do I need to install CRM Reporting Extension on SQL1 and SQL2 ?
Dynamics 365 Reporting Extension should be installed only on server with SQL Server Reporting Services. Apply update package for this components as well.
Regards,
