Liam's funeral is interesting because of his eulogy. The priest might speak many more words, but we hear him speak only a few phrases: "Taken too soon from the bosom of his family, a man of just 20 years and 6, Liam was well-loved by everyone he met. Receive this your humble servant. We pray that you may take his eternal soul into your care, Father." Liam was turned into vampire Angel in 1753. Not long before that, funeral orations were philosophical and theological in nature. They were often given in Latin for Catholics, in places where Latin was familiar to commoners. These eulogies said, more or less, "Now, the rest of you, try to avoid the sins of this sinner." But in the late 18th century, they began to focus on praise and memory of the departed. So the ceremony represents a transition between the old and the new traditions, just as Angel does himself.
Since Angel's real name is Liam, which is Irish for William, and Spike was known as William the Bloody, they essentially have the same name. This was intended by Joss Whedon and the other writers. James Marsters, who played Spike, can be found in many YouTube interviews and conversations with fans at conventions saying that Angel was the right boyfriend for Buffy, and that Spike was the bad boy, and therefore the bad boyfriend for Buffy.
Darla's line to Angelus "What we once were informs all that we have become" stands in direct contrast to Buffy's insistence in Doppelgangland (1999) that "a vampire's personality has nothing to do with the person it was". In the same episode, Angel almost corrects Buffy on this point, but decides better of it.