I hope you can understand everything from what I answer on your questions.
1.Grinding can get a bit hard on early levels and boring aswell but as the time progresses it gets easier, at least that's what I think, I hope others can confirm it, so overall it's not hard.
2.I haven't played pxg personally, but I believe clans are same like guilds in PA. So you can join one and have better time playing with friends together.
3.For now I think PvP is balanced, some pokemons still need some adjusting, but it's really awesome compared to the past. And yes, we had one recently, like 10 days ago, and they're not that uncommon at all.
4.No idea what is held but about the shiny part, yes. We have cloned and shiny pokemons. Cloned pokemons can be found at cloned island for which you need a ticket to enter and it lasts 48 hours, also it's only kanto pokemons there. While shinies are from johto and hoenn regions, and they can be found all over the map. There is a list of pokemons' shiny versions. Also their spawn is random after you kill their normal version, except for Eevee and Stantler, they have specific spawns. Eevee spawns at Cute island/Twin Rocks island, while Stantler spawns on Ice island 135 in Underwater complex.
And 5th, the most important, it's not pay to win of course. I've played this game for years and never donated before and I had fun times. Important feature of the game is getting a premium account, which can get achieved by buying 10 diamonds and giving it to NPC so you have additional features like flying, teleporting, access to new spawns etc. You can get your hands on those diamonds by donating of course, or just by buying from others players from in-game currency (which doesn't rely on donating). So you can have fun times without donating at all, especially it's not pay to win.
Yeah, I can agree on that, a lot of cool things are in the game and there are more being added always.
And no problem mate, we have a lot of tolerance for people whose english is not a first language, it's same for me too. And anyway, I hope you have fun in the game, if you have anymore questions just ask. If you are on Platinum, you can add me and ask me there for help also!
Sincerely, Shouya.