Black Kyurem - 1st atk, meh! DCE is rotated and most Special Energy post-rotation isn't anything good so makes this thing relevant. 2nd atk is fine. But good against fire decks since you can OHKO it for a single prized Pokémon. But how do we get the energy? Nagaquag and Welder? Its very awkward to accelrate W energy,that's why W isn't anything good right now. 3 Geodudes
This could be an option for non-GX decks, since they get the most value out of that ability. Maybe 2/1 Dedenne/Oricorio with some Cherish Balls. The attacks are stupidly weak for the energy cost, unfortunately.
Decidueye - I don't know what I feel with this Decidueye. Sniping 80 to the bench on a stage 2 for 2 energy in a format without DCE. Only good in Expanded with the GX. 2-3 Geodudes
Solgaleo - as a tanking card, its fine. Being a stage 2? Its pretty awkward. The main atk KOs Dedenne and most basic GXs but the atk costs sucks. How do we accelerate M energy to it? Plus, the prevalence of Welder makes M decks see less play because Welder makes Fire decks nuts in any way. Well, Metal types do have things like Metal Core Barrier and Metal Goggles for tanking. But then again, prevalence of Fire decks hinders them. 2-3 Geodudes