Well you could apply say a Lotus setup to a Mercedes, but all cars perform differently. If you take a setup and use it for another car, you're going to have to make some small adjustments to match the car's performance.
If you're looking for setups for online, look for setups for Red Bull, McLaren or Ferrari. When car performance is set to equal, the car will perform like these cars.
Setups can be saved. On the tuning screen, it's the far right option. Once saved, it can be loaded on any car on the track it was saved on.