If Larian maintains the current implementation of spell casting in BG3, Quicken spell is going to be seriously buffed.

In table top, there is a bonus action spell rule that prevents you from casting 2 levelled spells (non cantrips) outside of a single turn, with the exception being action surge.
https://roll20.net/compendium/dnd5e/Spells#content

Quote
A spell cast with a Bonus Action is especially swift. You must use a Bonus Action on Your Turn to cast the spell, provided that you haven’t already taken a Bonus Action this turn. You can’t cast another spell during the same turn, except for a cantrip with a Casting Time of 1 action.

I.e. if you quicken a fireball to use as a bonus action this turn, you can only cast a cantrip with your action the same turn.

In table top, quicken spell is best used by Sorcerer/Martials - who can quicken cast a spell and then still make a full attack, or if you have magical items/ability (i.e. Wands) that take a full action.

BG3 currently breaks this rule because there is no spell level limitations. You can launch a guiding bolt and a healing word in the same round. Haste is also implemented as an action surge, letting you cast a spell with that (this is normally not the case). I'm curious to see if this happens, and what kind of game-breaking combos we get out of it.