And I guess same could be asked about Los Santos Customs as there is the unique license plate that can be chosen with the app.
... hopefully it doesn't matter to you, or you haven't done this yet, but there is an issue with the custom plates as well as the LS part of the app in general.
The custom plate you choose will apply to ALL 3 character specific cars. So if you choose, for example "TheFrank" for Franklin's plate, it will go on Franklin's Buffalo, but it will also go on Michael's Tailgater, and Trevor's Bodhi. And there is NOT a way to revert this change that I can find. If you want their original plates back individually, you'll have to start a new game.
It does look like Rockstar will reset online plates, but not story mode plates.
You also cannot use LS customs on the ifruit app without choosing a custom plate, and you cannot do any LS customization's via the app without ALSO applying the custom plate.
I'm not sure if the plates apply to all 3 characters only when you apply them to a character specific vehicle, or if it also does this if you only use LS for the other vehicles you find or buy.
I DO know that I had to order it first, for the character car, and take that car into LS to have it apply (which it then immediately applied to all 3 characters cars), but I don't know if that means you can avoid universal application if you never take that specific car into LS again. But I'm not taking the chance as I have a really good playthrough saved right now.
But if you don't mind all 3 characters having the same plate, then you can order your first and if you change your mind later, you can also purchase more, but they will always apply to all 3 character cars at the same time.
Has anyone tested to see if there's a way to get different plates onto non-character specific cars? Or will it always change all cars with custom plates to the exact same one?