With Spike the demon doesn't have as much to go on. He loved and was loved by his mother. He had a comfortable life. So soulless Spike's nature largely comes from his issues with class and status. His demon rebels against the ordered social structures that rejected William, and so is more focused on mayhem and destruction. As for love, yes he can still love, but his relationship with Drusilla is co-dependent just as it was with his mother - a constant desire to please her and receive approval through that affection. His love is ultimately inward and self-serving because he is still playing out that Oedipal desire.
But - Spike hated the demonic mother. This hatred I suggest, was displaced onto Slayers. His demonic mother was a slayer - she killed the "good boy" by forcing him to kill her. In a sense, what we see is the abject(ion of the) mother literalised. IMO, it's not a coincidence that the first Slayer he kills says "tell my mother I'm sorry" or that Nikki was a mother. What makes Spike unique is the profusion of mothers. This gets around the thorny problem of the mother's fort/da - the good breast/bad breast - the phallic/castrating mother etc. He's able to separate them out into two different entities. What happens when he meets Buffy is the two Spike's (and there are - as I've described them - two) are united. He loves Buffy and hates the Slayer. It's this conflict we see coming to a head in S6. IMO, she has a similar predicament - a conflict of interests. She has feelings for William (As You Were) but can't reconcile this with her duties as Slayer - who's raison d’être is the killing of vampires. In S7 both work to put open water between their two selves. As they are in S11 - he probably still has a psychic structure that pertains to the hysteric but it's not as pronounced as it was and he's less prone to fetishization.
I won't go into what I think is the logic behind him getting his soul except to say he's driven by both love and hate and this isn't resolved or realised until part way through the trial. As for Angel, Spike's a romantic poet, what's the betting he's a humanist and his idea of the sublime is different to Angel's - isn't Angel Irish Catholic? Angel's problems are - as you suggest - no less Oedipal but it's a conflict with the father. I'd be inclined to look at to the other side of Freud's Totem and Taboo. I'd also consider a correlation between psychoanalysis and the therapeutic journey and Catholic Confession. I'd also look at his sister - Kathy (meaning pure) and ask why Angelus' "thing" is the rape and killing of nuns. I'd do all those things if I wasn't already procrastinating.