Why did you changed Crimson Akali to Infernal? What's the piont? She fits the idea of Infernal & Vulcanic themed skins line as well so. For me Crimson is fine and fits to that theme...
Because the skin has pretty largely been changed into a fiery deity. Crimson (and, in the case of your given language, Scarlet), are simply terms to describe the color red. They're both deep, vibrant shades of red, which really only worked for the previous iteration of the skin - which was a red palette swap of Akali's equipment.
But, since she's now a great spirit of living fire, it makes more sense to call her "Infernal" than "Crimson". While "Infernal" mostly refers to Hell/The Underworld/Inferno (hence Infernal Nasus being much like Cerberus, Hades' guard dog in the Underworld), it can also relate to something being "like an inferno" - a large fire that's out of control.
Although I kinda wish the thematic was a little less liberally applied - 'cause the Infernal skin line now includes a demonic hellhound, Nasus, a great armored minotaur, Alistar, who looks more like Scorched Earth Xerath, and a great fire spirit, Akali, who looks more fitting with the thematic of Firefang Warwick and Ashen Lord Aurelion Sol.
Don't change name of Crimson Akali, just put her in Infernal themed line n bind the conection to em by skin's lore.
Neon Strike Vi -> Super Galaxy
Underworld Wukong, TF should be in Death Sworn
Vulcanic and Infernal should be paried together
Nothen Front Swain is in Arctic Ops
Pretty sure Neon Strike VI is its own thing, separate from the Super Galaxy skinline. The biggest difference between Neon Strike and Super Galaxy is that Neon Strike doesn't involve mechs, whereas Super Galaxy (starting with Rumble and carrying on through every skin afterwards) involved mechs. (which is primarily in parody/reference to Gurren Lagann)
Lumping Underworld Wukong and Twisted Fate into the Death Sworn skinline wouldn't be ideal either - they've clearly got different aesthetics, whether noticeable (Twisted Fate) or more subtle (Wukong). Maybe if they were visually reworked to fit the spectral doom-cult aesthetic of Death Sworn...Maybe they could fit. And they'd need a name change.
As mentioned earlier, I think a distinction needs to be made in general regarding Infernal/Scorched Earth/Fire skins. It's hard to really say there's even a skinline or unifying thematic with those skins when Infernal Akali, Firefang Warwick, Ashen Lord Aurelion Sol (and likely in the future, Volcanic Wukong) share a visual thematic, but Infernal Akali's thematic clashes with the other Infernal Skins (Nasus/Alistar), who also clash with each other.
As for Northern Front Swain...Yeah? It makes sense, especially since his VGU where he was given the visual upgrade and thematic link to Arctic Ops Varus, Gragas, and Kennen. You'll also note that Arctic Warfare Caitlyn is part of that universe as well - though she is...Less-so fitting than the others. That'll almost certainly change in the future, though.
Not every skin with a roughly similar thematic needs to be lumped together into those similar skinlines. The smooth tech of Neon Strike looks similar to Super Galaxy, but doesn't belong there - unless the skin in question is bound to be visually updated sometime in the near future, where Riot can readily say "Soon™", there's no need to go throwing it into other skinlines. (Example: Resistance Caitlyn is in the same universe as Resistance Illaoi.)
