I saw some folks on the previous page talking about the names being split between being based purely on Spanish words (Fuecoco), partially on Spanish words (Sprigatito) and apparently not at all (Quaxly) and it got me thinking a little bit about the potential themes and ideas about what the starters may evolve into! Bear in mind I have no clue whatsoever about Spanish history, mythology or lore, in fact a fair good chunk of this I learnt from other folks speculating, but here we go!
I reckon Quaxly is going to have the theme of some sort of seafarer, which would explain why its name doesn't derive from any Spanish words - because they're either not originally from the region, or the theme that they travel so much doesn't pin them to any particular location. By seafarer you could go anywhere with it - a pirate, an admiral, an explorer? Spain had plenty of all of those from what I understand. I don't know what typing I'd give it - Water/Flying would be the boring choice, Water/Fighting would be pretty cool since we've not a Water starter with that typing yet (Samurott should've been a Water/Fighting type) and Water/Dark would make sense if you went the pirate route, albeit another mildly boring choice since Greninja already exists.
Sprigatito is based on partial Spanish - gatito refers to a kitten or a young male cat I believe? - which has me thinking it'll evolve either into a lion or an Iberian lynx! Iberian lynxes are a native to the Iberian Peninsula, which is the area the game appears to be set within (with Spain and Portugal) and Sprigatito looks relatively similar to a lynx as well (it's the tufts on the side of its head I think)? The combo of Spain/Portugal may explain why Sprigatito is only partially Spanish, although you'd think the sprig part would be a Portuguese word, so it's a flimsy explanation I suppose! The lion thing is because there's one on the Spanish coat of arms, and royalty usually were related by blood to other countries (hence explaining the partial Spanish yet again!). Typing wise I'm not too sure on, maybe Grass/Fairy or Grass/Psychic? I'd go with Grass/Psychic for this one, since lynxes have a small link to the supernatural and powers like clairvoyance.
Fuecoco is based on pure Spanish, so I think its theme will be similar. You could go with either the mythology thing (I don't know much about it though, but people have discussed various ideas which could work out?) or you could go with the food theme - the pepper concept seems quite cool? The spiciness is meant to be poisonous so you could do a Fire/Poison basilisk type, or Fire/Ghost since ghost peppers are a thing. You could run Fire/Fairy or Fire/Dragon for the mythology theme which could be interesting as well! I'm not too well-versed beyond that but that's just my thoughts.
As for the rest of the game, it looks pretty good! Open world seems interesting for a main series title, the areas look gorgeous so far and I think as time goes on they're going to reveal some really cool things. Looking forward to it!