I almost caused a TPK in a big fight right now by dropping ice storm on top of my team. Everyone still took massive damage, and it killed Shadowheart’s divine guardian which she had just casted. Read your spells carefully before assuming it’s safe to cast them on top of your party!
I think the ally limit that’s in the 5e tabletop rules isn’t implemented in the game. I just cast a Fireball on the whole party after summoning four ghouls and no one took damage.