This verse describes the practice to realize that tattva. The sages (munayah) — the jnanis cultivating contemplation, the yogis and the devotees — see that jnana of three forms by bhakti. Those who conceive of jnana as brahman realize (pasyanti) the jiva (atmanam) as the Lord (atmani). (tat tvam asi: You, jiva, are that, the Lord.) Those who conceive of the Lord as Paramatma see through meditation the lord in the heart (atmanam) in their heart (atmani). Those who conceive of Bhagavan see Bhagavan (atmanam) in the mind (atmani) and also directly in front of them (ca), and taste the sweetness of the Lord with their very eyes. The sages realize their form of the Lord by bhakti, which is first heard from the guru (sruta) and then practiced (grhitaya). The word bhaktya is used with its conventional meaning, indicating hearing and chanting about the Supreme Lord, Bhagavan. The worshippers of brahman and Paramatma must also perform bhakti directed to Bhagavan in order to perfect their own sadhanas. Jnana and vairagya mentioned in this verse are the two sadhanas for the jnanis and yogis only. For the devotee these two arise only from bhakti and indicate the loving nature of bhakti (because he loves the Lord he strives to know the Lord and shows distaste for everything else), since separate cultivation of jnana and vairagya are forbidden in pure bhakti:

tasman mad-bhakti-yuktasya yogino vai mad-atmanah |
na jnanam na ca vairagyam prayah sreyo bhaved iha ||

Therefore, for a devotee engaged in my loving service, with mind fixed on me, the cultivation of knowledge and renunciation is generally not the means of achieving the highest perfection within this world. SB 11.20.31

Or by mentioning jnana, vairagya and bhakti, the verse can express the idea that the devotees can realize through bhakti all the three aspects of the Lord: brahman, Paramatma and Bhagavan. Some who have that particular faith (tac craddhadhanah) develop the desire to realize all the three forms. Then, by bhakti, they can see all the three forms. Thus the goals of the sadhanas of jnana and yoga for realizing brahman and Paramatma will be accomplished only by bhakti.