Maybe everyone just already assumes this, but what I see is that your main panel, the “original” panel, has nothing connected to most of the branch circuits. The 90A breaker probably (can’t see it all in the pic) goes to the other breaker panel via the generator box which is a transfer switch (among other things). So in normal operation (generator off), the 90A breakers feed the new subpanel where your generator supported loads are. Any loads that remain on the original panel are probably not supported by the generator. Although I can’t read the rating of the remaining breakers in service, several have wires that suggest they are large loads that would potentially overload the generator.
The question remains where the main breaker is, but you should be able to monitor the whole shebang with two SCT019 (YHDC) on the feeds to the original panel… Those should be available soon from OEM with 3.5mm plugs or you can source them elsewhere and attach plugs.
As for monitoring, SCT019s are configured through the browser based menu on IotaWatt, which should also be available soon. There are 14 channels total available on IotaWatt, configurable for a variety of CTs from a WiFi browser based app. Basically plug-and-play.