Not all of them. Different Buffy comics have various storylines and timings. Some could fill in gaps from earlier seasons or offer alternate perspectives rather than strictly following after Season 7.
Buffy began as a television show and only later was adapted into comics. So, it wasn't a comic initially. The TV series gained popularity before the comic adaptations came out.
Buffy's relationship with Spike in the comics varies. Sometimes they have significant interactions and may even be romantically involved, but it's not a constant throughout all the comic series.
It varies from comic to comic. Sometimes they have a romantic connection, while in others, their relationship is more complicated or not existent at all.
Buffy does have some science fiction aspects. The show incorporates magic, demons, and other fantastical elements that are common in the genre. However, it also blends in elements of drama and horror.