The BRZ is only available with one engine. It's a FA20 naturally-aspirated 2.0-liter flat-four that will happily rev to 7,500 rpm. The engine is mated to a slick Aisin AZ6 six-speed manual, but the A960E six-speed automatic transmission is available. We wouldn't bother with the automatic transmission unless your personal situation requires a self-shifter.
There are two different opinions on this engine, and both are valid. There are those who feel that it's asthmatic and requires forced induction in order to fully unlock the BRZ's potential. To others, it's simply part of a perfectly balanced driving machine. We accept both arguments as valid, but we've always enjoyed the BRZ as is. Yes, it's not the most powerful engine, but we love the immediate throttle response that you can only get from a naturally-aspirated engine. The suspension is also tuned for low-speed hooliganism, and doubling the power just makes the BRZ more of a handful.
Subaru and Toyota designed this car so even ham-fisted enthusiasts can get the tail out at 30 mph. It even has an in-between setting for the traction and stability control that will help you slide a bit. That same system will eventually intervene, which means you don't end up in a YouTube fail video compilation.
The manual transmission is a joy. Throws are short and positive, and the pedals are perfectly spaced for heel-and-toe action. If you couldn't be bothered, you have the automatic option. It's nowhere near as fun and slower than the manual. Having said that, the self-shifter is tuned for fun driving. It will even rev-match when you shift down. The rest of the drivetrain is sublime. All of the power is sent to the rear wheels only, also known as right-wheel-drive. The front end of the car is nimble, and the steering is wonderfully communicative. Even though the BRZ is razor-sharp, the suspension never feels too hard to live with daily. One thing you have to keep in mind is sticking to the OEM tires. There will be more affordable or grippier options, but the BRZ's inherent balance relies heavily on the right tire/wheel size and choice.