In “A Special Type of Choice of Object Made by Men” Sigmund Freud discusses normal sex while in “‘Civilized’ Sexual Morality and Modern Nervousness” he discusses normative sex. His earlier works might be said to discuss libido at the nuclear level, the undifferentiated bisexual drive and its interaction with its host’s family. These two later works take up the same question but from the external point of view, from the cultural perspective. In other words Freud here discusses the sublimated form of sexuality: love.
Love to Freud is not just a cultural euphemism for normal sexuality. His early works discuss sexuality as a drive easily appeased since it has no inherent intention but adjusts to whatever is available. Those papers are on infant sexuality, which is still in development, and thus can indeed choose anything as its object. It still has the flexibility to mold itself around said object.
What we forget is that adult love is conversely very discriminating. As “A Special Type of Choice of Object Made by Men” points out there are subtler conditions of love than sexual appeal such as jealousy and hostility. These often hark back to the childhood Oedipal drama just like sexual object-choice but they explain the more nuanced details that comprise love versus sex.
In “‘Civilized’ Sexual Morality and Modern Nervousness” Freud elucidates the social norms which civilization imposes upon us animals—normative sexuality has very little to do with natural/normal sexuality. Most basically normative sexuality describes abstinence until marriage. This arrangement is purely utilitarian and yet appears to us to be romantic, all in the name of supposedly irrational love and devotion.
As Kinsey revealed, normal sex and normative sex are thoroughly divergent. In striving to meet the love ideal individuals repress their sexual impulses and sublimate their libidinal desires. Only a tiny percentage of people can sublimate their sexuality perfectly into socially acceptable avenues. The rest of us become perverse and/or neurotic.