Hi, Dariush
It seems you're asking about RStudio Server Pro, and you can find the load balancing configuration instructions at https://docs.rstudio.com/ide/server-pro/load-balancing.html#configuration-1
To answer your first question:
Server configurations (i.e. contents of the /etc/rstudio directory) must be identical.
So, yes, you must list all the nodes in every config file.
To answer your second question, take a look at Access and Availablity. You have the option to define either a single master or multiple masters in RStudio Server Pro.
Note that the instructions for RStudio Connect is different, and you should refer to the Connect admin guide at https://docs.rstudio.com/connect/admin/load-balancing/