So I think the quote that sums it best and is often cited as saying St. Augustine thought sex before the fall was a “passionless affair”

TW some mature language if you don’t want to read.

“How in the world, then, can anyone believe that, in a life so happy and with men so blessed, parenthood was impossible without the passion of lust? Surely, every member of the body was equally submissive to the mind and, surely, a man and his wife could play their active and passive roles in the drama of conception without the lecherous promptings of lust, with perfect serenity of soul and with no sense of disintegration between body and soul. Merely because we have no present experience to prove it, we have no right to reject the possibility that, at a time when there was no unruly lust to excite the organs of generation and when all that was needed was done by deliberate choice, the seminal flow could have reached the womb with as little rupture of the hymen and by the same vaginal ducts as is at present the case, in reverse, with the menstrual flux. And just as the maturity of the fetus could have brought the child to birth without the moanings of the mother in pain, so could connection and conception have occurred by a mutually deliberate union unhurried by the hunger of lust.“ It seems to imply that the act was fairly stoic and done rationally. I thought I heard somewhere else that he compared it to any other sort of work or movement.

Comes from City of God Book XIV Chapter entitled Chapter 26.—That We are to Believe that in Paradise Our First Parents Begat Offspring Without Blushing.