I think most hybrid water heaters offer a heat pump only mode where they won’t use the immersion heaters, or only when you’re almost out of hot water. The big box DIY stores often link to the user manual which would tell you whether a specific model offers this feature.
I don’t know how you’d set it to run only when you can best make use of the cooling. Since you’re on net metering you won’t have a time-of-day rate when it’s cheaper to heat the tank.
Sounds like you’re checking PV output from the manufacturer’s portal. You might want to consider installing an EmonPI2 or an Emporia Vue or similar to get more detail about what’s using electricity. See emonTx V4, emonVS in North America. You should be able to see how much energy each heat pump uses, and get an idea about whether experiments succeed in reducing energy use.
You could read Heat Geek’s article on why not to zone and decide whether it makes sense to turn head units off in unused rooms.
You may want to measure humidity levels. Mini-splits get high SEER ratings by not running very cold and so not using much energy to dehumidify, but you could run the house hotter in summer if it’s drier inside and still be comfortable. It may be worth running a dehumidifier to reduce the electricity the heat pumps use.
You may also be able to adjust the set points to make the upstairs do more of the cooling and let it fall to lower floors, and the downstairs do more of the heating and let it rise to upper floors.