There are some differences between supported platforms.
On iOS and macOS there is a synthesiser which can play instrument samples (not using a standard sound font), and various synthesised waveforms including 3 types of click (for a metronome) and sine, square and triangle with adjustable parameters. With the synthesised sounds the pitch to frequency can be determined by a function so your app can support different temperaments.
On Android there is no SeeScore synthesiser so if you want to play the score you will need to use another synthesiser. It is possible to write a MIDI file from the playdata and play that using the Android Media Player, which is what the sample app demonstrates. However it is important to note that the sound quality of the Android Media Player is very poor, and there is no possibility to change the sound font.
On Windows it is possible to write a MIDI file from the playdata and play that using the Windows Media Player. The sample app shows how to do this.
The score layout should look identical on all platforms with a given version of the SeeScoreLib