See my post on this thread.
You will need to rename the folders as needed every few days, maybe every 5 days. Update and launch the game with the vanilla folder renamed obviously to GTA 5. Then after that exit the game, put in scofflineonly in the launcher commands, exit the launcher, copy the egstore folder from the vanilla updated to the modded folder. Rename the vanilla to something like GTA 5 vanilla and rename the modded to GTA 5. Then get back into egs launcher. Make sure you have as -scofflineonly. Then launch. Rinse and repeat. Obviously you need to have update game automatically off.
Post explains step by step.