Rockstar's policy regarding mods in GTA V is unforgiving if it touches multiplayer, inciting a lot of fear and caution. Fear, however, is not enough to stave off ambitious projects such as The Pinnacle of V.
Describing itself as a "massive game enhancer modification", The Pinnacle of V is a combination of visual enhancements (including an ENB) as well as various Quality-of-Life enhancements that make the city of Los Santos feel more vibrant and realistic along with the gunplay and vehicle handling. The feature list is too much to go over in one article, but I will include a brief overlook of the main pointers.
Starting with the visuals, the mod revamps everything ranging from the weather visuals to the textures in the game, bumping up the texture quality of many aspects to 4k. Some carrier vehicles are also replaced with real counterparts, such as ones for Coke and Pepsi. In general, new textures are being created (as opposed to textures just being upscaled) for various portions such as foliage, the night sky, blood and more.
An ENB, which also comes with this overhaul, can be seen as a custom piece of software that takes over the graphics rendering that Direct3D normally takes care of. ENB's are known to allow a user to specify all sorts of effects such as bloom, depth-of-field and such. Practically, this means very little to the common user until the ENB is configured to enhance their game's visuals. Many modern games have ENB's made for them, and if you run a pretty powerful system, it may be worth looking into one for your favorite game if you would like some more visual fidelity.
Besides their textures, vehicles have also gotten a rework regarding their handling. Be it on land, water or air, the models have been modded to provide realistic deformation along with top speeds, weight, handling and much more. The page states, "Finally you can drive around Los Sonatos in a vehicle that doesn't feel like a toy!" a most promising prospect indeed.
NPC's themselves have seen some improvement as well. Relationships between the police, gangs, animals and the players have been changed to create a more lively environment. Gangs and Police are said to battle it out on the streets and allowing players to enjoy their encounters with animals much more. More notably, you can finally stand closer to pedestrians for a longer time without them running away, a feature that has already been introduced before with GTA V modding in the past, but finally finds a place in a grand overhaul.
Population levels have been increased as well, but specific to both the area, time, and day of the week. This is meant to simulate realistic city rush hours and a more lively feeling to the city. All the DLC vehicles will now also spawn in traffic naturally as well.
It would be remiss to have a GTA V overhaul that doesn't touch on the gunplay and general carnage. All the original weapons have been rebalanced with realistic recoil, spread and much more. The bullets travel at realistic speed instead of being hitscan (instant hit) and certain materials can be shot through, such as thin metal and wood.
But more interestingly, bullets can now break apart fences and other objects that in the past were unbreakable.
If that alone wasn't enough for the carnage-intent among us, grenade explosions have been likened more to the effect of an RPG and fires have been improved to increase their length and spread and have an improved overall look along with the materials it touches. Finally, weapons have also had their audio redone, promising more immersive custom sounds.
The FAQ answers some of the more in-depth questions. The mod will run with version 393.2, but a version equal or older than 463.1 will require the user to not use certain specific files to prevent a crash (see the FAQ for which ones). Furthermore, the mod will largely not work online. The ENB and Reshade will work, but the game file modifications will not allow you to play online and may put you at risk of getting banned by Rockstar. There are also instructions on circumventing the game's tendency to overwrite the modifications as well as help for people who are only interested in certain specific parts of the mod.
The Pinnacle of V looks like it wants to squeeze the most out of your system visually, and tie the gameplay with it to provide a very realistic and enjoyable, perhaps even challenging environment for you to cause carnage in. Perfect for the GTA V enthusiast who has little interest for GTA Online.