The art and style look really great (love it), the balloon shapes are better placed on the second version though I like the shapes they had on the first one the most (the spikes did felt like more than one character was speaking though).
You can check some tips from Nate Piekos at his website Blambot (he is a pro letterer and also has different comic book fonts available as well).
You can read the tips here:
https://blambot.com/pages/comic-book-grammar-tradition
https://blambot.com/pages/lettering-tips
He also just released a book about lettering that could be worth a read too:
https://blambot.com/pages/the-essential-guide-to-comic-book-lettering