I just finished TURKS -The Kids are Alright- yesterday (don't judge me, I didn't really want to read it because the Cases of... aren't really great litterature ok, but ToTP actually made me want to read it), and I truly think that the ending of this novella is the true ending of AC/C. There's just no ifs or buts, it's something they obviously couldn't do in the movie - lol NPCs no one knows about but they're part of their daily lives - but to me it falls straight into it.
I also really liked the description of the TURKs, Evan made me laugh because of how similar he is to Cloud (it's like a script commentary from Nojima himself really), and all in all, this is a great way to cement the story between the end of FFVII OG and the end of ACC. I even spotted a few characters from this novella that we could see pop up in Remake (in Nibelheim and Icicle Inn). it was just an enjoyable read, and I put my comments about it here because it ties so much into ACC IMHO. If you have only 2 novellas to read to understand ACC, then certainly CoT and TKaA are the to go books (since Cases of Lifestream are so short I don't even count them).