That is a very good question and I'm glad you asked it before buying the hardware !
I do not have direct experience with the PowerMonitor 500 or 1000, but I've used the 1402, 3000 and 5000 so I know it's worthwhile to verify any assumptions you make about the communications features.
The Red Lion DataStations cannot act as an I/O "Scanner" on EtherNet/IP, nor can they directly read Assembly Objects or other CIP Objects. They can read and write ControlLogix native tags, as well as PLC/SLC/MicroLogix data tables. And of course they have good Modbus RTU and Modbus TCP drivers built into Crimson.
My reading of the PowerMonitor 500
user manual is that its normal communications with a ControlLogix are over I/O connections to the Assembly Object. It does all of its configuration comms with Modbus/TCP. So that's a bit of a weird mix of protocols that likely comes from the PM500's origin based on a third-party product.
It is likely that you could use a PowerMonitor 500 with the DataStation, using Modbus/TCP only. The summary of data tables starting on page 57 of that user manual makes sense to me.
The
PowerMonitor 1000 has a lot more variety of interfaces and protocols. The serial port supports DF1 and Modbus and even an ASCII console.
The Ethernet port is relatively low powered (10 Mb/s, half-duplex) and supports Modbus/TCP, native EtherNet/IP objects including an I/O Assembly and various data Assemblies, and PCCC data table emulation.
The most useful for your purposes is the "PCCC data table emulation". This allows the PowerMonitor 1000 to emulate a classic Allen-Bradley PLC data table. The addressing table in Appendix A of the user manual is very useful.
For example, the Volts/Amps/Frequency monitoring data is presented as Data Table address F21:0-19.
In Crimson or any other HMI software, you would configure the PowerMonitor 1000 target like a MicroLogix 1100/1400, rather than like a legacy PLC-5E or SLC-5/05.