Benchmarking doom eternal

So, considering the discussion in the comments, and my opinion, possible causes of the FPS drop and screen tearing for the specific game in question, CS:GO, would be (in order of likeliness)

• Corrupt configuration files on CS:GO. (OP already reset them, discarded)
• CSGO or Source Engine update issues (No updates were released at the time of the incidents)
• Busted drivers. (OP already reinstalled them so, discarded)
• Broken GPU fan, so it throttles down to prevent damage. (Op checked them, so discarded)
• Dirty GPU contats. (OP already cleaned the card, so discarded)
• Tweaking fps_max value. (Already done, discarded).
• Nvidia GeForce Experience causing issues. (OP uninstalled it, so discarded)
• Steam Overlay causing issues. (Op disabled it, so discarded)
• Windows update messing with OS. (Op stated that no updates occurred before the incidents)
• Nvidia HD Audio causing issues. (OP uninstalled it, so discarded)
• Busted Video Card (By OP's comment this turned out to be the culprit)
• Busted RAM (Unlikely)

At the time of this answer we don't have specific information about performance in other games, OP specified that the screen tearing was occurring on Borderlands: The Pre-sequel as well, but we don't have specific performance data. On the other hand Furmark stress tests didn't crash the card, but the issue in the games persist.

Given that information the only option we have left is a somehow damaged Video Card, the solution would be to fill a RMA, as the card was recently bought. I suggest contacting with the manufacturer instead of Amazon or Nvidia. The manufacturer (if professional enough) would give you a tested card, guaranteed to work, while Amazon will give you another boxed one or a refund if you are a regular client. Nvidia will do nothing they only build the chipset. I've had a reasonably good experience with EVGA for example, not sure about other manufacturers.

The book titles refer to other games that came out during the 1990's as well as franchises that are owned by Bethesda.

1. Daikatana - Superfly Johnson is a sidekick to Daikatana's protagonist, Hiro Miyamoto, and accompanies you throughout much of the game. Daikatana was directed by John Romero, one of the major figures in the development of the early id software games including DOOM I & II.
2. Duke Nukem - The name "Dork Norkem" is a play on words of Duke Nukem. The unflattering name of the author may refer to the rivalry between id Software and 3D Realms (the developers of Duke Nukem).
3. Devil Daggers - an indie game insipired by Doom/Quake.
4. Unreal - the Liandri Mining Corporation is the organiser of the Tournaments in the Unreal setting and acts as an antagonist in many of the games.
5. System Shock 2 - the Von Braun is the spaceship in which SS2 is set, and the primary antagonist of the series is the rogue AI SHODAN.
6. Half-Life - Unforeseen Consequences is the third chapter of the game, the location where these consequences originate is the Black Mesa Research Facility.
7. Deus Ex - UNATCO (United Nations Anti-Terrorist Coalition) is the agency that the protagonist, JC Denton, initially works for. In dialogue the name is always pronounced "u-nat-co" as a word rather than initialised. The game also has a scene which became a minor meme involving the discovery of a bomb.
8. Wolfenstein 3D: Spear of Destiny - A prequel to the game Wolfenstein 3D, both of which were developed by Id Software, who also developed the original DOOM.
9. Rage - A game by id Software in the similar vein to the Fallout series.
10. Quake series - Stroggs are alien invaders that are bad guys in Quake 2 and Quake 4 and are playable characters in multiplayer games (e.g. in Q3 Arena). Their logo is also present in original Quake on so called Strogg Crates.
11. DOOM, original flavor - Flynn Taggart is a known alias of the original Doom Guy, primarily in the novelizations of the original games which... deviate from the game canon, to put it mildly, hence the mention of retconning.
12. Commander Keen - Dopefish is a large green cartoony fish featured in the game.
13. DOOM - Tei Tenga is a planet or a moon which is mentioned as off-world mining place in original Doom and in 2016 Doom reboot.
14. The Ultimate Doom - Thy Flesh Consumed is the final episode in the game.
15. Prey - The title here refers to the on/off nature of the cancelled sequel to the original Prey. It might also refer to the minor controvesy about if the 2017 game is a reboot or a sequel.
16. Fallout - The protagonists in the Fallout series are called Vault Dwellers, and an item in various Fallout games is the 'Wasteland Survival Guide'. This guide would be useful to them to survive the nuclear wasteland.
17. Fallout - Nuka-Cola is a beverage in the Fallout universe.