********************settings.xml********************
in here you will find folders with files in them to help speed up GTA 5
there are three settings.xml files settings_low.xml runs fast and still looks good
settings_super_low.xml lowers settings a lot but has lowered some users FPS in game
settings.xml is just like settings_super_low.xml but made to work with out lowering some users FPS in game.
when replacing the settings.xml don't forget to make a backup and rename one of the files from the settings xml
folder to just settings.xml and replace.

the Screenshots folder will help show you in order to set up the control panel

********************how to edit settings.xml********************
the settings.xml needs to be edited be for it will work
you need to put your video card name in this line
<VideoCardDescription>YOUR VIDEO CARD HERE</VideoCardDescription>
and for your screen resolution you can change it here or in game
<ScreenWidth value="800" />
<ScreenHeight value="600" />
and if you need to run the game window change this here to a 1
<Windowed value="0" />
some users have gotten better fps with DirectX 11 in GTA 5 if your video card/GPU supports it you should give it a try.
some users have gotten better fps with DirectX 10.1 in GTA 5 if your video card/GPU supports it you should give it a try.
<DX_Version value="2" />
this will set the DirectX for the game 
value=2 (sets the game to DirectX 11)
value=1 (sets the game to DirectX 10.1)
value=0 (sets the game to DirectX 10)
if you need to find your video card name you can do this by going to start then to Accessories then System Tools
and then click System Information
from here you will click on components then Display
your card name will be listed as Adapter Description
there are all so other ways to find this
NOTE:this is not the settings.xml editing this file will do nothing

********************NVIDA********************
open the NVIDIA Control Panel and in 3D Settings then go to
Manage 3D settings and click on program settings
click the ""select a program to customize" and select GTA5 if it does not show click add and if Grand Theft Auto V does not show up click
browse and look for GTA5.exe
set Anisotropic filtering to off
and every thing saying Anti-aliasing set to off and Anti-aliasing - settings to none

set Maximum pre-rendered frames to ""use the 3D application settings
multi-display/mixed-GPU acceleration to single display performance mode
and if power management mode shows set it to prefer maximum performance

this setting can help you get more FPS and lower FPS so try to see what works best for you
set shader cache to off (if your FPS is lower by doing this set it to on)

set texture filtering -Quality to high performance
set vertical sync to off
then click apply

********************AMD/ATI********************
open the Catalyst Control Center and click on Preferences and then Advanced view and then to Gaming and click 3D Application Settings
set mipmap detail level to high performance and set 
wait for vertical refresh to always off then click save and 
select the GTA5.exe
then click apply

********************COMMANDLINE********************
this will just make it so you dont have to edit the settings.xml and add your video card name.
you add edit and add more to it all commands can be found here
https://support.rockstargames.com/hc/en-us/articles/202518358-Available-Command-Lines-for-GTAV-on-PC