It's not pay 2 win in the sense that you can't get limited items that are better and unachievable for people not spending money on the game like some games I played (APB:Reloaded being one example).
I prefer that smaller grass patch also as they are the same encounters except it's closer to the pokemon centre and also has 3 trainers which you can vs seeker for a little bit of added $$$. Really good guide though helped me a lot EV training my kingdra.