7th and 9th chords are my favourite. They give a song a night-time, soulful quality and in themselves, you have everything you need for a song.
You will probably find this easier than Someone Like You. However you will still need to get the technique of playing both melody and arpeggio on right hand. The illusion is that the arpeggio is there all the time, but in fact it is alternating with the melody, to fill in ‘holes’ in the backing of the song.
Don’t worry about the timing too much, it can be quite free, speeding up or slowing down, within reason, is quite OK.