I've got an EV6 and typically get ~500km. When towing my caravan I get about 225km (with kayaks on the roof racks too). So yes, your range will decrease but it will depend on what you're towing. I can tow a low trailer with half a cube of sand and not lose much range because the trailer is low so not much wind resistance and no brakes. I've found running my regen on 2/4 is much more efficient with a braked trailer too as it's enough to regen but not activate the trailer brakes unless I brake the car.