I've never found grass useful, especially not in the beginning. Way worse than water. The flying type helps against early bugs but water is still the more well-rounded type. I also find water to be the most solid (haha) foundation for a team.
Maybe I just feel Rowlet is a bad choice because I love Oricorio and already decided I just neeeed a Sensu Style one on my team.
Lovelovelove the way Popplio is going. Not a fan of the first one but the evo is adorable and if the leak is correct the final stage will probably be a new fav starter.
I agree Water is better than Grass, but does that mean Popplio is the automatic choice? There are some nifty Water Pokemon to catch, so you might be better served catching one of those depending on how early you can get them.