I've always added Lubegard to our transmissions, even on premium ATF's. As Steve mentioned, I recall Trav's testing with LG and how it lowered trans temps. Definitely not snake oil. IMO, I would use the Red.
I've never had an issue using it, put it in at least 10 different vehicles. No experience with Dex VI apps, but I've used it with Mercon LV, Maxlife, Amsoil, SP-III, Mercon V, and T-IV.