..from the article: 

The series will initially be written by Bryan Edward Hill with art provided by Gleb Melnikov to bring this crossover to stands. The Executive Editor for BOOM!, Jeanine Schaefer, had this to say about Buffy and Angel crossing paths for the first time in this new comic universe:

“Everything in Buffy the Vampire Slayer and Angel has been leading to 'Hellmouth,' the first major comic book event featuring Buffy and Angel. But Angel #5 is where the pieces all start coming together. We’re excited for fans to see just how far we’ll go in this reimagining of two huge pop culture icons—because when Buffy and Angel finally meet, it’s not going to go the way you expect!”

(emphasis mine)

(This probably means they’re going to be antagonistic toward each other. To put sixteen-year-old Buffy through a romance with a vampire while she’s trying to save Xander!vamp is not a good look. Boom!Angel seems to be super avoiding romance or female companionship of any kind, which, good. It implies he knows about his curse’s loophole. And there’s that ridiculous he’s going to try to kill her and vice-versa thing because please.)

https://www.bleedingcool.com/2019/06/19/boom-teases-top-secret-buffy-comic-for-hellmouth-crossover-via-variant-covers/

Some more info about the variant covers for “Hellmouth” - all of this is coming out in September, so they really are hyping this up.

https://www.comicsbeat.com/boom-studios-september-solicits/