In most sets, gold indicates a rare card, orange or red denotes a mythic rare, and silver signifies an uncommon card.
Once the Hero deck mostly emptied its hand by turn 4 or so, then its luck was spent
As you pointed out, the difference between Pokmon EX and Pokmon GX is that the former ones are always Basic whereas the latter ones are always the stage they are supposed to be [1] (except for Tag Team GX cards which are also always Basic)
Some would be reprints and some would be new designs
I have ways to ramp with Your Fate Is Thrice Sealed, ways to cheat big creatures from my deck into play with A Reckoning Approaches, and a powerful scheme to get big planeswalkers like Garruk, Apex Predator or Ugin, the Spirit Dragon in Perhaps You've Met My Cohort
Gold foil should be smudge-resistant