Define best. All game modes have different top decks, and every player has their own variation.
Yes, there are better. But nobody can tell you what they are but yourself.
What's the chance? Very good if you buy those cards off the market, not so good if you buy something else. As for packs, anything that includes older Sakrohm, Piranas and La Junta. So anyone but new bloods. Morphun isn't in packs, you need to do his mission. Neither is Smokey Cr, you need to win one off elo, as he is too cheap to get from lottery