VATs in Fallout 4 is the Vault-Tec Assisted Targeting System used to shoot specific parts in the turn-based combat system with a cinematic combat experience. In fallout 4 your character benefits from a damage reduction of 90% from all incoming damage during it similar to Fallout 3. This Fallout 4 Mod will help you turn on full-time VATS-Assist.
How to turn on full-time VATS-Assist
Bethesda has strictly made a barrier on the overuse of these VATs in order to handle the mechanics, thus, purely focus on your stamina in the game. With this Turn-Based Simulator Mod, you can use VATS, again and again, all the time, without waiting for AP to regen. This Mod will also remove all the restriction over teh game mechanics like the 90% damage reduction in VATS, so basically you take as much damage if you play turn based as in real time making it look a lot more balanced.
You can find the Link above for downloading the Turn-Based Simulator Mod. Once you add this Mod, you will also get +1 PER on account of all the sensors and circuitry, plus act as a bright headlamp for when you need that. This Mods – full-time VATS-Assist works with the headlamp slot of Power Armour and mining helmets as it adds constructible assemblies of sensors and circuitry which works with your PipBoy.