There is a large difference. Love story leads you down the path of a couple who grows closer together through their exploration of one another's shared desires and you grow as a couple to find more and more each day that you didn't know about one another. This path also includes romance options for another woman, Claire's sister, and you as the player will have choices to pick from. Stay faithful to your gf, choose the sister overall, choose both, and so on. All while writing about it in your blog eventually opening up other options for more love interests.
The optional Ntr path will be about you as a couple who learn to experiment and try new things, further developing either a consensual open relationship, or even go so far as creating to possibility to be shared involuntarily eventually. This opens possibilities for cuckqueen, cuckold, ntr, sharing, and so on. All avoidable, or optional. All also while writing about it in your blog, inviting in more possibilities with others who discover the blog or know you write it.
The overall shared story is a mystery waiting to be solved involving eventually the entire town, and the neighbors next door who will be dug into a lot more in the coming release.