I saw a question about how many systems you can manage through Ops Center. This is an important question when you're planning a deployment, or looking at expanding an existing deployment.
In general terms, an Enterprise Controller can manage up to 3,000 assets. A Proxy Controller can manage between 350 and 450 assets, although you'll get better performance if there are fewer assets.
The Sizing and Performance guide has more detailed information about the requirements and sizing guidelines for Ops Center.