The difference between Add-on and Replace methods
I just need someone to help me understand what is the difference, and which method is the best to use.
Replace: A car, usually from the real world, that replaces an in-game car from the game. The new car will then take on the properties of the original car's name. ie You can use the original name to spawn it & it will automatically spawn in traffic like the original car did.
Add-on: An add-on is like an extra car that installs like a dlc. You still have all the original cars that came with the game. Add-ons are easier to install & if required can still be made to spawn in traffic.
Add-ons are the preferred method & I would say they are the best option.
A Replace car mod is a car that replaces a car that is already in the game
Example: You take the Phoenix & replace it with a Trans-Am. Once it is installed correctly (handling.meta entries, vehicle.meta entries & if done completely also carcols.meta & carvariations.meta enties. ie You take the settings the mod author gives you & use OpenIV to find the meta files, extract them, open them with Notepad/Notepad++ & replace JUST the settings for the car you want replace. In this case the Phoenix) then when you spawn 'phoenix' the Trans-Am will appear. The Trans-Am will also now appear in traffic instead of the Phoenix.
An add-on car mod will install similar to a dlc. It will be an extra car you can spawn & you will still have all the vanilla cars as they are in the normal game (it can also be used to replace an in-game car using popgroups.ymt. See below). Add-ons are much less work as they tend to come fully packaged with all the meta files required in the right place in a dlc.rpf file (usually in a folder of the name of the car ('16challenger' for example)). You then take the folder containing the dlc.rpf & put the folder in:
\Grand Theft Auto V\mods\update\x64\dlcpacks
Always use a 'mods' folder! Do NOT edit your default files!
The file structure will then look like this for a 16challenger example:
\Grand Theft Auto V\mods\update\x64\dlcpacks\16challenger\dlc.rpf
All that is left to do after that is add an entry to dlclist.xml for the new add-on car (near the bottom of dlclist.xml but above '</Paths>')
The bottom of dlclist.xml will then look somewhat like this:
<Item>dlcpacks:\patchday14ng\</Item> <Item>dlcpacks:\patchday15ng\</Item> <Item>dlcpacks:\patchday16ng\</Item> <Item>dlcpacks:\16challenger\</Item> </Paths> </SMandatoryPacksData>
Note: Sometimes an entry is also required to be added to 'extratitleupdatedata.meta'
That, as with what I have previously mentioned, is usually explained well enough by the mod authors & shouldn't be too difficult to follow.
You can then spawn the car in-game using the name the author provides. 16challenger in this case.
Spawning Add-ons in Traffic:
An add-on can still be spawned in traffic if required by editing 'popgroups.ymt'. You will need a decrypted version of the file first. Luckily this mod: https://www.gta5-mods.com/misc/southern-san-andreas-exotic-popgroups-ymt-803cba20-ebff-4a21-82a7-b0d70ab9a39a has one.
Once you open the file, near the bottom you will see entries like this:
Very simply, to spawn an add-on you either create a whole new entry (using the same format as the ones that are there) or you replace the name of a car you want to replace (phoenix, sabre, vigero etc) with the name of the add-on car (16challenger etc). The line will now look like this:
You then, using OpenIV, put 'popgroups.ymt' here:
Grand Theft Auto V\mods\update\update.rpf\x64\levels\gta5\popgroups.ymt
overwriting the existing file.
Note: If there is no popgroups.ymt in the folder path above you can search for it in OpenIV by pressing Ctrl+F3 (also 'Tools' tab> 'Search' works too)
Essential: Always, always, make backups. Either of the entire .rpf or at least of just the files you plan on editing. Always!