This is a harder question to answer because the limit has more to do with the traffic that you are expecting to flow through the Universal Print Connector by ezeep. Do you and your users print a lot and often? The appliance has to process all your print jobs, rendering and outputting them to the correct printer.
The answer is that you could have all your printers in your network but realistically you should have up to 30 printers to be supported by 1 Universal Print Connector appliance.
When connecting to your local, USB connected printers then you can physically connect 4 printers to the Universal Print Connector appliance.