I think this is the fake evo that is closest to what we are going to get for Grookey.

Unless it's something related to sound/drums, everything seems to point that it's gonna be a samurai (hairbun, stick), some say that it will be a 'waifu' starter, but Delphox isn't precisely female, just a bit feminine, and there are examples of samurais with feminine traits like Kenshin.