Here's Part 3 in my new Forgotten Games series on my blog.
https://www.pigames.net/store/blog.php?entry=2832
You pick some good shit.
Bureau 13's setting was close to what we got with the original run of Delta Green - cell structured government anti-weird agency, lost a lot of members after one specific incident, lot of "do what you can, here's some equipment, good luck." I thought Delta Green did it a little better, but that was mostly through presentation and subject license - the Bureau 13 art was a little on the cartoony side, Delta Green's was not and had the "this is a Call of Cthulhu product" gravitas.
Nick Pollotta wrote a set of novels based on his own version of Bureau 13, which turned the outfit into a group with access to unspeakable amounts of resources and they were not afraid to use those resources. Real gung-ho and kick ass, which is sometimes exactly what you want.
On Abyss, it was an RPG extension of a miniatures game also done by Global Games. The miniatures game was called Inferno: Battles of the Abyss. A buddy and I made an abortive attempt to get into the miniatures game for a bit - there were little horde footsoldiers that fit five on the old-style square Epic bases, then sergeant units that were slightly bigger, lieutenants bigger yet, and archfiends that were enormous. The boxed set came with a small background book that was fairly interesting too. I bought the RPG book years later, flipped through it, couldn't really get any of my normal players enthused about it. Global Games did something else. Legions of Steel? Space Hulk knockoff with some more bells and whistles, if I'm thinking right. Did play a few games of that because we were apeshit crazy for Space Hulk (1st edition). It was fun.