Ah yes, the action economy.
Laughs in Spell + Hasted Spell + Quickened Spell + item that give you an extra Bonus Action spell (or the BA cantrip "Shove") + Action Surged Spell + Fast Hands Bonus Action (quickened spell, obviously) + probably another item(set) that makes spells more powerful and/or gives you another action to cast a spell.
At this point you're just TRYING to find something broken, though, and if you're hardcore looking for it you're going to find it--it's impossible to fully balance a game of this magnitude. JUST having access to other spell lists isn't in and of itself broken; hell, WotC allows it, depending on choices. Ultimately we're still going to run into issues of only one conc spell, and only one spell per turn without other things stacked on top of that. I think it's fine, tbh.
I mean...yeah? This was half real and half hyperbole. No one is actually going to take 3 levels in rogue just to get another bonus action for their spellcasting and I have no idea if you can Quicken two things per turn in BG3. Let alone the (hopefully?) non-existent "item that gives you another action to cast a spell."
That said, even in 5e RAW it's fairly common to take 2 levels of Fighter for Action Surged Spells, and Potions of Speed aren't that rare. So 3 to 4 leveled spells in a turn isn't that hard to pull off for a sorcerer in BG3.
...which I'll use to get slightly back on topic. Ideally multiclassing into 2 levels of Fighter will slow your spell progression and levels of spells known.
