Your service is 300A. Probably OK with 200A mains CTs but could be something I don’t see.
Can’t read the subpanel breaker capacity, but guess it’s <= 100A. You can monitor the whole subpanel usage from the main panel by putting CTs on the two poles of the breaker. To monitor specific loads in the subpanel you will need to either extend the CT leads or add another IoTaWatt. If the EV charger is connected to the subpanel, you may want to do that.
The loads you mention: A/C and pool appear to be fed from the main panel, so that’s OK.
You will need to decide if you want to mount the IoTaWatt in a weathertight box on the exterior or inside on the other side of the wall. The electrician will probably have an opinion on that. Depending on the subpanel capacity, he may want to connect the EV charger to the main panel anyway and so would need to lead the cables through the wall.