(PDF version attached, as well as full-res images in a Zip file. The PDF should also be higher res than this too, as I think Civitai has a hard limit on image size in articles.)
Work on this article is in progress, I'll try to keep adding to this whenever I get time.
Style showcase – Ratatoskr:

Conditional styles:
Extra_artstyle, monochrome

This one requires any colour tags to be removed to function properly, but with monochrome "extra_artstyle" is both quite distinct from the standard version, and is quite consistent in its differences. Monochrome works with any other style, and generally all styles should work together, but this style specifically looks different due to the fact all of MGE Vol 1’s references are greyscale, while Vol 2’s are coloured.
Extra_artstyle_alt, monochrome

This one only works with monochrome, as all the references are also such, and functionally it’s pretty much the same as the standard “extra_artstyle” but with slightly different shading. I’d say it normally has more shades of colour overall, but the difference is largely negligible, and the tag is more-so to keep the references separate to the base style for consistency’s sake.
Reference sheet, multiple views

This one generally requires position and perspective tags to be specified in addition to “multiple views”, such as “from side, from front, standing, sitting”, in this case. Duplicates are common (as demonstrated here), but the more specific you are, the less chance something will mess up.
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WIP Styles:
(No good examples yet, but might work under specific circumstances/with luck)
Sketch – Inconsistent due to the number of different artists covered.
Lineart – Slightly more consistent than “sketch”, but not by much
Doujin/comic – Similar to “reference sheet”, in the sense that “multiple views” and position/perspective tags are normally required. Borders and spacing are inconsistent though, and the order of each scene is random.
Cover-art – The effect of this one varies, probably just a lack of references for this one on my end.
Theme showcase – Succubus:


Conditional themes:
(Less consistent, and limited performance with certain clothing)
Regal theme

This one performs quite well with some clothing options, but doesn't work with more modern things like hoodies, shorts and so on.
Order theme

This one has varying effects, mostly because it's used for both "soldier-themed" monsters like the trumpart, valkyrie and the main slime-carrier girl, as well as things like the angel and cupid.
Undead theme

This one tends to generate things like skulls and spikes with decent consistency, but the intended effect is supposed to be more akin to "tribal", with torn and old-looking clothing. It also has a tendency to generate colored skin, as most references have it.
WIP themes:
(No good examples to show yet)
Modern theme - Doesn't have any consistent effects due to the variety in what constitutes "modern", and the fact some monsters that aren't covered by it still have modern-looking clothing, like the high-orc's thighhighs or the holstaur's overalls.. Modern clothing options still work fine, but the theme tag doesn't.
(More to follow, WIP)