Hold them in ANY wallet of your choice. Only thing to make sure is that YOU OWN THE PRIVATE KEYS (ie, you can export and view them)
With that you can add your future BTG in ANY wallet that will support BTG.
And yes, Jaxx works. Because you have the keys. In the off chance that they don't support BTG you can use your keys to get them in any wallet.
RE: How I'm going to MAKE MONEY with the upcoming FORK! (Step-by-Step Guide and Insider Secrets)