The Asi Loader is essential, the Native Trainer, no, but the latter gives you immediate access to various cheats for GTA 5 how to teleport, the fast running and super jump.
The package Script Hook V includes both the Asi Loader, the newest to the most recent version of the Native Trainer. (typically, the path to the root folder of GTA 5 is in “SteamApps->common->Grand Theft Auto V” if you have the Steam version, the path is similar to the version on the Epic Games Store)