Yes, it seems like you can pick whatever path you'd like. That would be very interesting in terms of what Levels and Pokemon the Gyms have and how they vary with game progression. I still want to see if the rumor is true about there being a Gym for every type. I doubt it, though. Some are starting to believe Gym Leader Teams will have themes rather than be focused on one specific type, sort of like a weather team here and something else there.
Graphics seem okay to me, but I don't really know what to look for with that. You seem much more knowledgeable than myself in that regard, Mike, so I'll take you on your word. As long as the story is good, I will be happy.
It will definitely be more like Arceus than Sw/Sh, but I'm sure they do forward some of the stuff from the latter. The co-op gameplay seems interesting, but I doubt it will truly be like traveling with friends. Like your game has to still active all battles for your player and not the other, right?
Also, it is confirmed it will be a past versus future theme. Professor Sada is derived from the Spanish Word for Past, Professor Turo is derived from the Spanish Word for Future. Plus, the Cover Legendaries, who appear will be ridable motorcycles, names translate to Ride of the Past and Ride of the Future in Japanese.