It depends upon which Donne. There are two: the early Donne focuses on the physical union of the male and female, while the late Donne focuses on the spiritual union of man and God.
Both Donnes are intellectual. Neither are realistic, really. The early Donne is definitely not realistic: he uses metaphysical conceits, a harsh meter, and a complex tone. In "The Flea," for example, he urges society to leave he and his lover alone because he thinks the world is coming to an end. This is highly emotional and not realistic.
At age 43, Donne became a minister for socio-economic means more than any real spiritual or artistic conversion (the Church of England thanked him kindly). His intellectual correspondence with his parishioners was not realistically achieved: he still used the complex metaphorical language of a poet in his homilies. He intrudes and digresses in his highly stylized sermons and poetry of this period.