The first step of understanding the poetics used in Gurbani would be to understanding the different between laghu (short) and dhīragh/gurū (long) syllables. View this video to see how a couplet (doha/dohra) is formed with this understanding:  Unfortunately there are no English texts which help explore poetic meters in Gurbani. If you know the Hindi script you can use: Rupert Snell, A Braj Bhasha Reader: https://hindiurduflagship.org/resources/learning-teaching/braj-bhasha-reader/ Otherwise Kahn Singh Nabha's Gurchand Divakar is the best resource: https://archive.org/details/gur-chand-divakar