>>28949340So I compiled all of the starter stats in their base forms and their final forms. We you look at them you can see base forms DO NOT change what is the highest and second highest (the third highest can change, but usually doesn't).
Thus, since we know Litten is the fastest, followed by Rowlett, finally Popplio, Rowlett has 23 hp at base, suggesting highest hp, while we know popplio has high hp, sp attack, sp defense, and defense, but awful attack and speed.
Thus Popplio will be a tanky pokemon, probably more specially inclined.
Rowlett will be the middle one probably, with middle speed, attacking stats (lower than sp attack that Popplio but higher than Litten and vice versa with attack), but highest hp. Or it'll be a more physically defensive pokemon with middle speed.
Litten is probably going to be like most fire types, high speed and attacking stats, a good mixed attacker.