I think we will have to realize any S&S game still based on D&D, and this game certainly only lightly skins 5E, cannot come close to the true tropes of S&S magic.
First off, sorcery is not just a tool you can rely on and use uncontroversially. It's a fearsome dark power you never use lightly. (If you use it willy-nilly you have invariably "gone too far", and you have become a despicable wicked monster).
So you always need swords for protection. You would never plan to just use magic.
This is in direct opposition to D&D, where spellcasters are made to be equal to fighters in combat (just using different tools, that are equally controversial - which is to say, often not controversial at all).
This is the first hurdle a true S&S conversion need to address.
Second: S&S magic is in direct opposition to might. That is, sorcery corrupts and degenerates the man. If you are a foul sorcerer, you are seldom if ever equal to a real man. (At this point, I'm not going to dance around the fact men are the default warriors of S&S. I will just note that female sorceresses have it easier since they're not losing anything precious to them)
And truly heroic might always beats magic. This is distinctly quite the opposite of most D&D.
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What you want of a S&S system is warlocks sacrificing their mental and physical health for untold powers and wickedness.
You want spellcasters not relying on direct magical destruction for protection. They can hire sellswords, or they can conjure up physically powerful demons. Conan seldom has to face magical death rays. The odd fireball, yes, but that's something you can shrug off. I'm talking things he's defenseless against.
With one big exception: enchantment spells. Things that mess with your mind is your big weakness. Which becomes an even bigger problem when those cultists that use them are high-Charisma females...
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Everything bleeds, and therefore you can kill it if you're just
heroic strong enough. A spell like "Wall of Force" has no business existing in S&S unless you give it a "bend bars, lift gates" DC to smash.
There pretty much needs to be a Strength-based way to dispel any magic you can physically interact with, leaving illusions and enchantment tricks the spell category to really fear (as a muscle mountain of a hero).
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In short, you want magic to work more like how desperate people turn to Nurgle-worship in Warhammer. From a
player's minmaxer's viewpoint, it makes zero sense to allow your character to be inflicted with pustules and rotting diseases, just to be able to cast the odd disgusting spell.
In S&S no wholesome
hero barbarian will ever want anything at all to do with magic.
And the point is: history gives them right. That is,
the game system itself should ensure might beats magic.
From a PC charbuilding perspective, Magic should
never be the minmaxed choice. Magic should not even be a regular alternative or be presented as equal to might. Magic should, at most, be presented as the "edgy" controversial choice you choose just to be different.
You turn to magic because you're bitter about not being strong enough, manly enough. Not because it offers a cool alternative way to build a ass-kicking character.
A real S&S game forces you to make real choices. It's like a game where you don't assign scores from an array but instead you roll up stats randomly. The higher you roll, the more of a hulking brute you want to create,
since you can - you're the epitome of creation for a man.
If you roll low, the game system offers sorcery as a double-edged compensation. You need it to be able to compete, but you will always be tainted, compromised by trucking with dark forces (which magic invariably is).
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A good start is to limit hero PCs to half caster magics. I don't care if your 6th level character is an Eldritch Knight or a Fighter 3/Wizard 3, just as long as you aren't a Sorcerer 6.
This is a very simple efficient and balanced way to ensure the above remains true: that no man can rely on magic alone.
Then make sure any NPC warlock doesn't have direct damage spells, and you come much closer to S&S magic. Summoning and enchantment spells are fair, and I see no reason why buffing or debuffing spells need to be prohibited (since those place the focus on the impending contest of might where it should be).
Damage spells that bring more atmosphere than outright overshadow melee are okay: burning hands or witch bolt or what have you. Visceral spells that require the caster to dare come close and get dirty.
The spells most removed from S&S are the "intellectual" spells - the spells that a psionicist could use. A telekinetic spell that simply lifts Conan into the air to hang defenseless, for instance. Or Forcecage. Such spells either don't exist at all, or just serve to make Hulk angry.
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Saying this as a reaction the recent discussion about spellcasting classes. From my vantage point, that discussion fusses over minor variations in a still fundamentally D&D-centric game. What needs to be done, if you're serious about discussing how to emulate S&S, is to shuck out the very core of D&D, and replace it with a core true to S&S.
If you're not prepared to do that (and believe me, I do understand the appeal to simply use D&D for your S&S), I really don't care about the small details. Bard or Druid, who cares? Both classes are inherently D&D, so both will do well for a lightly-skinned S&Sian game of D&D.
Don't get me wrong, 5E already is a good candidate for S&S reskinning (certainly more than d20).
You just need to do a bit more than argue whether Druid or Bard fits best...
