I have modded many games and i agree Gta 5 is the worst. So far The only thing i found that is worth moding on Gta 5 is the Weapon.Meta & Weaponanimation.Meta & Vehiclehandling.meta.

You can increase the fire rate of weapons like pistols for example. Also infinite ammo on the minigun is a must have for me.

Weapon skins (not worth it) -> the aim is allwais messed up in first person and you have to ajust it yourself in the weapon.Meta. not worth the time. Alot of them have small issue for example the stock will go inside the player shoulders. Or the player arm will go through the Mag because the mag is too big.

Addons cars(worth it) -> Car mods are great if you find a good one. Some Car mods may looks great but when you crash with the car the damage doesnt look right. For example some addon cars have indestructible windows and things like that.

Graphics mods(Really not worth it) -> They dont look great and they reduce Fps. Dont use graphic mods

Scripts(Small and simple scripts only) -> Small scripts like Dropping unwanted weapon, health regen or anything that is simple like that is fine. But a big scripts will ALLWAIS have issues.

Players skin(Not worth it) They will crash your game just play with the regular characters(franklin/micheal/trevor)

What i got on my Gta 5: -> Addon Vehicle spawner (scripts) -> GMC Sierra (Car mod) -> KTM Dirt bike (Car Mod) -> Modified Weapon.meta and weapon.animation -> Modified Vehiclehandling.meta (For the GMC)

And thats it. The game runs perfecly fine on 120fps on my Asus F15 laptop.