My experience, I've always used Ethad to fly into Abu Dhabi and rented a car to drive to my hotel in Dubai. From Abu Dhabi International Airport to Armani Hotel/Burj Khalifa/Dubai Mall area is about 1 hour 15 minutes, You'll be probably driving on Sheikh Maktoum Bin Rasid Road, which is a four lane highway. The roads are safe. If you have a rental, it will warn you about your speed, about 120km. When you drive to refill you car, a gas station attendant will pump your gas for you.
If you rent a car at Abu Dhabi Airport, renting from Sixt, a representative will use a whatsup app and contact you and meet you outside the baggage claim area. On the day you return the car, you will contact them and they will meet you at the terminal to return the car. From the other main rental companies, they have a small rental car area, remember where this is at, they do NOT have signs around the airport. It was frustrating looking for the car rental return area, if you are in a rush and trying to catch a flight, you'll probably be late. Leave some time. Good luck