The above info relates to After The Fall. That was written by Brian Lynch and the story planned out by Whedon & Lynch. Thus like Season 8 its considered canon.
As for "Aftermath" Whedon had zero involvement, and its not by the great Brian Lynch. Its a 5 issue arc written by Kelly Armstrong, and though she claims to have seen Angel the TV show, by reading it it really does seem like she and the artist have never seen a single minute of the show.
It's pretty bad IMO. Awful art (why does Angel look like the Hulk muscle wise? What the hell is Angel wearing throughout?) Terrible & very clunky dialoogue, panels that don't sync up, crap plot, badly written dull new charatcers, etc.
Kate Lockley comes back in it, but her reunion with Angel is over and done with in about two panels, and the way she looks and talks throughout the book isn't anything like the Kate in the show.
I gave up after the first three issues and just skimmed the last two in the comic shop. Glad I did too, and I certainly won't be wasting any money on the TPB.
This isn't just my opinion either, most folk on the SlayAlive boards agree it kinda sucked.
So After The Fall yay. Aftermath nay.