As far as I know you can use either one, but I am not sure if it’s possible to set some data like rgb values with homeassistant.turn_on, but you can always test and see for yourself using the developer tools - services page. It’s in the left sidebar and looks like a remote control.
In the service data (json) you just write the unit like this: {"entity_id":"light.one_device_etc"}
The states page <> is good to find the names of your units.
I would add them up to the same group and try with homeassistant.turn_on + {"entity_id":"group.the_new_group"} and see what happens.
homeassistant.turn_on should work and automatically call the correct service for the component. Can you post the config for the group as well as the automation you’re testing with?
Ah, so you have the wrong entity for your zwave switch in that group. The zwave entity itself is really only useful for seeing if it’s awake/asleep/etc. You need to find the associated switch or light entity.
If you look at the list of states in HASS, you should see something along the lines of switch.intermatic_ca3000_wall_switch_switch_4_0 in that list. Use that in your groups.yaml file rather than the current one you have. Then the homeassistant.turn_on service will correctly turn them both on.