Hi!
Ive made an integration for Solax, using the official Solax cloud API 2.0.
It supports multiple and singe inverters (micro inverters and “regular” inverters)
Read all about it here at Github: Solax Cloud API 2.0 at GitHub
I fetches all your inverters, and also creates a new “System Total” entity that combines all inverters, and gives you a total overview of your system.
That way you get total system sensors, without having to create anything manually.
It also calculates the inverter and system effiency etc.
It supports a single account (Single API token).
Total System information (this system contains 3 micro inverters):
Single inverter info:
Ive tested it for 2 months, but as you know, all systems, setups etc are different, and we all have limited time, so any bug fixes or updates might be slow, if there are any 
Happy holidays!