Austen strategically matches each couple by issue, personality, and mannerism in a way that stands out almost as if scientifically planned. Her relationships in Pride and Prejudice are like formulas that, when combined, form interesting reactions.
In the case of Lizzie, we know about her behavior through her actions and through her words, but as far as feelings go, she leaves us wondering and waiting for her to say big words, which she doesn't.
Darcy, her counterpart is the same way. All we know of him is through his actions and words, but both Lizzie and Darcy are too much complex of characters for us to expect them to form a romantic bond. They did, however, and, in the end, we still are left wondering "how did it happen?"
Charlotte and Collins are the joke of the story. Collins is into himself so he needs someone who is GOING to be into himself. Lizzie rejected him and his ego, so his most logical shot would be the plain and empty headed Charlotte, who even admitted that this is a good move for her to do in order to make herself somebody.
Bingley and Jane, both quiet, both unsuspecting, both going with the wave, got together in what one could consider far from a passionate romance, a soap-opera type encounter. Bingley and Jane really do not make too much noise in the story.
Wyckham and Lydia however do make up for all the noise Jane and Bingley left behind. These two were an ill match made on purpose to show the weaknesses of an ill breeding on the side of the Bennets. Lydia, a ticking time bomb, fell for Wickham's uniform, more than for the soldier inside of it. Wickham is as shallow and libertine as anything, so he eloped with her, ruining her reputation in society. Both still careless, Darcy intervened to provide money to marry them off for the sake of the Bennets reputation (and knowing now that Jane was his friend's love interest), and had them return to society. Lydia still clueless, Wickham, still shallow.
No relationship experiences dynamics for Austen, as they remain the same sentimentally, but once their characters are put together, the readers can see how they matched strategically from the beginning.