You can using taxi or hire a car/motorbike with a cheap free Vung Tau is crowded only on holidays, it is way more spacious than Saigon. Unless you want to go as far to White Villa or Light House, you can walk around and see the city, enjoy local. Grab/Uber are not available in Vung Tau, you can go by Taxi 8-15k VND per km or rent a motorbike is best way to travel. From Vung Tau, bus picks up/drop you right at the alley. Hoa Mai, Toan Thang buses... are available every 15-30min from/to D1, Airport takes 2h-2h30min. You can also travel by hydrofoil to D1 faster but not recommend in rough weather. If you need any help, feel free to let me know.