How does the concept of multiclassing damage scaling of spellcasters.

[Padoru]

I am making a storm spellcaster build and I am pertaining to the guide below. However, I dont yet fully grasped the concept of multiclassing damage of spellcasters. The guide doesnt really tell what spells to take.

The Sorcerer class makes it confusing when selecting a spells. What I could understand for now, is that the guide tells that my (main) damage will be based on INT and on scrolls because I have a two dip in Wizard class (2 Divination Wizard) and 17 INT.

So what I am currently doing now is ONLY taking all QoL, control spells, and buff spells (Haste, fly, misty step, etc) every time I level and dip a Sorcerer class (8 Storm Sorcerer) but NO DAMAGING SPELLS in the Sorcerer side, even though the Sorcerer class provides Lightning spells, because my CHA (Sorcerer spell attack) is low.

So, I delegate all my Sorcerer spellslots for QoL and utility spells. Then Wizard spellslots for damaging spells (leaning through scrolls) like chain lightning, lightning bolt, call lightning.

Did I understand it right? Did I miss some info?

I assume this guide, specifically the storm cleric one (2nd), relies on wizard spells which means I wont take any damaging spells on sorcerer class?
https://www.reddit.com/r/BG3Builds/comments/1fgsdc8/full_honor_mode_party_comp_wet_lightning/

[Chaosolous]

Each class uses it's own spellcasting ability. That's how that works.

[tazman1]

spell damage is static based on the dice rolls.

there is a school of wizard that will let you add your Int bonus to the damage of evocation spells. in which case that would impact all evocation spell you cast regardless of what list they came from. Its might be going off your INT because its higher and therefore the one giving you the best bonus to DC and spell attack

[Thomas D.]

I wont read the guide also plenty of build guides are mediocre or work only when you want to play a very narrow specific way. This sounds pretty much like that. But if you have specific question to that specific build, you could ask questions directly there.

You can build a Sorcerer as pure Control / Support Char then it might look a bit like what you describe. But you can also build them perfectly as killing machine (the Sorc is best suited for this).

For scaling: All spell casters scale the same way, you get higher level spell slots (only exception are Warlock which have a different kind of spell slots that dont stack with the spell slots from other classes).

Then some classes have special abilities that add to the damage, like for example Metamagic from the Sorcerer (especially Twin Cast and Quicken Spell). Other classes give you other benefits and if you want 2 of different classes you have to multiclass.

Further spells on their own dont scale, they are fixed (but some abilities of the class might add additional damage or allow you to cast them at multiple targets / multiple times like the Sorcerers Metamagic). The usually way to make spells stronger later on is to upcast them (casting them with a higher level spell slot). Sometimes / often casting lower level spells with a higher level spell slot is even more powerful than casting a high level spell slot, I personally tend to prefer lower level spells except if a higher level spell gives you really a lot and is definetly better.

The exception are cantrips. They scale with player level (no matter if you multiclass or not) and build correctly they can be on par with leveled spells or even outclass many of them in most situations (even level 6 spells).

But when you multiclass you have to pay attention to the spell casting attribute. If you for example multiclass Sorcerer with Bard its a no brainer because both use Charisma, just pump Charisma. Same goes for example for Cleric and Druid both use Wisdom, just pump Wisdom.

With Wizard + Sorcerer it gets a bit difficult because Sorcerer needs Charisma while Wizard needs Intelligence. For Defensive / Supportiv spells this rarely matters. But for Offensive, Debuff, Control or Damage Spells this is very important, because you need a high Attribute to be able to cause the effects / do (full) damage with them while you would fail with a low Attribute. In such cases you usually pump one Attribute and use offensive Spells primarily on that class which the Attribute belongs to and use the other class for supportive / defensive Spells where it often doesnt matter how high the Attribute is.

The thing is that the Metamagic of the Sorcerer is so good / strong / powerful that you often pair him with other Casters, even if you primarily play another caster. Usually you dont have any drawback doing so (except not being able to get level 12 in the other class) because you still gain the same amount of spell slots (they stack) and you can just use the spells of the other class for offensive things, so you can for example go full intelligence in a Wizard / Sorc combo and use the Wizard spells for offensive stuff plus augment them with the Sorcerers Metamagic.