Hi Jill,
If you have a second ArcGIS Server instance federated with Portal, you can still publish services to it. You just cannot publish a hosted feature service. You will be able to publish map services, and feature services (if the data resides in an Enterprise Geodatabase).
For hosted feature services, the data is copied from it's source location to the ArcGIS Data Store, and then a service is created. In this case, the data is now disconnected from it's original source (say for example, an enterprise geodatabase feature class). Therefore, if you were to make edits to the enterprise geodatabase feature class, they will not be reflected in the hosted feature service until your overwrite the service. Also, if you make edits to the hosted feature service, they will not be written back to your enterprise geodatabase. I typically recommend to customers they publish relative static data, i.e. county boundary, as a hosted feature service.
If data is updated frequently, you would want to publish this service to your other ArcGIS Server instance with the option to Reference Registered Data. This will not make a copy of the data, but create a service and reference the original data. Therefore as soon as you update the source data, the service is updated immediately.