I gave some thought and I think I sort of have an idea of how the various "occult magic user" tags/jobs are conceptualized, though I have difficulty... phrasing those in a coherent manner. Still working on those. Though basically the TL;DR version is:
1. Witch: Macbeth-esque “Double, double toil and trouble” female occult magic user. Usually wears a distinctive wide-brimmed 'traffic-cone hat' in combination with dark-colored traveling clothes (e.g. robes, cloaks, billowing capes, 'practical' dresses).
Archetypal examples: Weird Sisters (Macbeth), Granny Weatherwax (Discworld)
2. Wizard: 'Wise' and 'experienced'-looking occult magic user. Often old and has a long-flowing beard. Actual appearance/clothes vary, but the following examples provide two general archetypes.
Archetypal examples: Gandalf, Merlin (not the dickwizard version!)
3. Sorcerer: Powerful, 'confident-looking', 'virile' occult magic user. Often has propped-up high collars (Warning: TV Tropes link). As a further contrast to the wizard, generally has neatly trimmed facial hair (often sporting a goatee). Often has an 'exotic' appearance.
Archetypal examples: Doctor Strange (Marvel)
4. Sorceress: Powerful, 'confident-looking' (read: sexy) female occult magic user. Usually has some sort of exotic headgear instead of a hat, to further contrast with the witch archetype. Often has an 'exotic' appearance.
Archetypal examples: Maleficent (Disney)
5. Mage: Generic occult magic user. if you have an occult magic user that can't fit them into any of the above... mage is the usual fallback. Because of this, there are no archetypcal examples.
Examples: Black Mage (Final Fantasy I), White Mage (Final Fantasy I), Ricken (Fire Emblem: Awakening)
Currently trying to type a... better-explained version of the above, though it's still WIP.
Anyway, not sure if we need all the above tags, but in hindsight it'll be a good idea to at least keep Witch and Wizard. I suppose we can populate Witch with enough Marisa examples if we must.
Mage is also nice to have, but it does (and will) get 'polluted' very often with all the characters with "mage" as part of their job names. Still... if we want to, mage (as a discrete fallback generic occult magic user tag and not a catchall tag that the others imply to) is salvageable. So...
1. Toss in the Vivi Ornitier posts that qualify (hat seem a bit undertagged for Vivi) and we prolly get two hundred posts. Black Mage has more but this requires careful sifting because any black mage that appears overly female is a witch instead. And Final Fantasy XIV ones (different outfit) being sorceresses.
2. Toss in ricken_(fire_emblem) hat, another thirty.
3. Toss in white_mage robe... 374. And white_mage has more that qualify because their robes are kinda undertagged. Might probably be too much though.
4. Red Mage is a big toss-up. Some count as witch, some count as mage, some count as sorcerer... kinda a headache. Good way to find examples to feed to other tags though.
5. The Touhou witches (the race/youkai) also count, at least when they're overtly using magic. Ironically enough despite their 'race'. So, ~alice_margatroid ~hijiri_byakuren ~patchouli_knowledge magic -witch_hat has nearly 400 examples (probably ~300 that qualify, and maybe around 150-200 'decent' ones). Fortunately enough, this doesn't flood the tags with Touhou examples.
And I suppose 'Eastern' occult magic users that don't quite fall under onmyouji or miko (nontraditional ones too) miiight also fit under mage, but this is probably not a good idea. Yukari overtly using magic doesn't really fit, and neither do, say, Taoist practitioners.
(The Yukari/Eirin/Okina-style occult magic user seems to be some sort of syncretic mix between both Onmyouji and Taoist practices. Not overtly any of them though, but there are some elements of both. Clothes-wise they tend to wear, well, almost everything, but they usually also wear some kind of Chinese-style tabard on top, often with trigram markings and/or Eastern-style constellation print)
NWF_Renim said:
As for sorceress, there is a type of depiction that I think could be separated out from other conventional female spellcasters that may be worth using the label "sorceress" for. While I think witches and wizards are generally associated with more conservative clothing that covers the body, there was also that common depiction for of female spellcasters in fantasy as wearing very revealing clothing that tended to stand in contrast to the stereotypical wizard, mage, or witch. Examples: post #4451201, post #3023912, post #2681722, post #4065113, post #594918. The style probably originates from fantasy stories designed to appeal to young men as the female spellcaster wears very revealing and form fitting clothing.
It's mostly because the sorcerer/sorceress archetypes project "power". And "confidence". Both tend to use bolder colors than their witch/wizard counterparts. The male version also generally cares more about his appearance (compared to the sagey-philosophy "I don't give a damn" Wizards) and tends to wear 'tailored' clothes (though still occult/robe-like) and have well-trimmed hair and facial hair.
The female version also projects a similar air of "power" and "confidence", but because of well... 'gender conventions', this tends to manifest as "dresses provocatively".
Though... speaking about those two... most Fire Emblem characters with the "sorcerer" class (or an advanced version) will probably count as as either one of the two, depending on gender. tharja_(fire_emblem) tiara -alternate_costume -fake_animal_ears -nude -rating:e alone has 318 examples that mostly count for sorceress.
(Funnily enough... for Tharja I needed that many excluded tags to exclude the posts that depict her in various states of undress, or stick animal ears on top, to the point where she longer resembles a "sorceress".)
Though, speaking about Tharja, it's interesting to note that her clothes share many similar traits with Mona's. The main difference is their headgears. Just swap their headgears, and now Tharja looks like a witch while Mona looks like a sorceress.
Edit: Continuing:
On witch/wizard hats:
The usual witch_hat is as mentioned, a wide-brimmed 'traffic-cone' pointy hat (like the sorting_hat). Usually colored black, sometimes purple. The pointy end is usually somewhat floppy, at least compared to wizard hats. The main issue is that, well, oftentimes the witch_hat is only a witch_hat because it's being worn by a witch (and ironically at the same time the witch is often only a witch because she's wearing said hat). Stick a man into the same style of hat, and it becomes a wizard hat. Take it off completely... and it becomes, well, just a pointy hat.
Though they are some hats (like Marisa's) that are heavily associated with a certain character (or a group of people), to the point where people will immediately think of witch hat even if no one is actually wearing it, because it is still "worn by proxy". And relatedly, if the hat is decorated in a certain style, often with hatpins and feminine frills & ribbons (though not to the point when it starts to lose the 'occult' look), most people will also think witch_hat, because they're likely imagining a witch wearing it.
For wizard hats... probably two types in general. The first one is basically the same style as the ('unflaired'/undecorated) 'traffic-cone' hat that witches wear. Like what Gandalf has. This is usually only a wizard hat because it's being worn by a wizard (ironically enough, like some of the witch_hat examples).
The second type is the 'Merlin'-type wizard 'thinking' hat. Tall narrow cone, stiffer tip (compared to the floppier traffic cone one), narrow brim or no brim. These are also often blue with moon and stars decoration. Sometimes they are green or red. This second type of hat is what Danbooru has defined as a wizard hat on the wiki.
So yeah, witches and wizards are often defined by their hats, and their hats are defined by the witch or wizard who wears them... with both happening at the same time. Prolly Discworld has some quote to that effect in a more pithy manner.