Yes. For example, if you have a HD file, and you want to use it on an iPhone, then select the iPhone preset. Turbo.264 HD will scale down the file to match the perfect resolution for the iPhone, which is much smaller than HD resolutions.
Turbo.264 HD will not take a file with a smaller resolution, and scale it up to a larger resolution. For example, if you add a iPhone-sized file to Turbo.264 HD, and choose the 1080p export format, then the resulting file will not be 1080p - it will still be iPhone resolution.