Yes you can have both options fitted.
The auxiliary “water” heater can be controlled from Mercedes Me and also has a egg shaped digital remote which can switch on and off and also set the times for it to come on, limited to 50 minutes. The temperature is set through the climate control in the vehicle and if set at its lowest can cool the van with air in at air temperature, but not chilled air - ie it dosnt switch on the A/C.
The auxiliary air heater has an oblong remote that switches the heater on and off. It is linked to the center console that runs the roof, fridge etc and temperature can be set through that. As it has a thermostat if you set the temperature it will control the output to that temperature and is not time limited.
I’ll post some pictures when I get a chance.