Hey Rrrr,
No, with Group, you cannot create a device other than “default” ones, based on class of capabilities.
If you want a device with multiple OnOff and Energie, you need to create an AVD from the Device Capabilities app.
You can then create an AVD with multiple buttons and a numberfield=energie, and configure the status through flows.
This is how i am re-building my grouped devices: for instance, my lamp-group in the hal im gonna make a AVD which in the Device Tile will show the time left before the group is turned off by a Chronograph timer.
And it will still react to being pushed on the device tile: Having all lights in the hal and it’s time in one device!