I like a lot of the ideas in this class. The use of pact-magic like casting and class specific options are unique and set it apart. All of it is just very poorly balanced, and there are a lot of things not accounted for. The big ones; A half-caster should not get fighting styles at level 1, being a half caster means that they can only be a half-martial class and getting almost all of fighter level one is too much, this is why ranger and paladin both get their styles at level 2. The choices of fighting styles are quite odd too, a lot of the flavor and art depict characters with swords and melee weapons but 2/4 of the fighting styles are for ranged weapons only. I also don't get adding a custom fighting style here, it feels too powerful but even that aside you're adding more complexity. Their spellcasting feature is still called 'Spellcasting" when by the multiclassing rules in the phb they conflict with eachother because this progresses more like pact magic while all the other 'Spellcasting' features progress similarly. It is also not addressed if/how this interacts with a warlocks pact magic. In that same vein the fact that they end up with the same number of spell slots as a full warlock is pretty suspect. They are one level lower but especially for this style of caster quantity easily trumps quality. If one was to treat this as a half-pact-magic feature they would never actually get a 3rd spell slot much less a 4th. Warlocks get their 3rd slot at level 11(the same level your class does) and with the normal spell slot progression for half-casters they never reach level 11 casting in the class they are 'half' of in terms of casting. The Cell feature is both too central to the class and too powerful. That kind of area control is rivaling a lot of first level or second level spells, and the number of uses they get is rather high. It being so central to the class means that thematically they are inflexible. Even if I am only multiclassing into this class for 2 levels because I want to add some int based casting to my fighter I have to incorporate this feature into my roleplaying whereas any other multiclass could easily be flavored to more closely fit who I am as a character. The subclasses get too many features. This is a little nitpicky but ranger/paladin subclasses only get 4 features whereas this gets 5, two of the subclasses get 6. The fifth(sixth) one could easily be removed as 3/5 of the subclasses get extra attack at 5, giving them all extra attack would be much easier to handle for a dm/other party members. 5 subclasses is also a bit much, this isn't a powerlevel thing but a complexity one. there is a lot going on here which makes playing, playing alongside, dming for, and balancing this class very difficult.
Overall I like the ideas but I don't see many dm's allowing this class in their game unmodified, I as a player and a dm would not feel good about playing or allowing this class in a game. That alone is a huge the class can't be used unless it's allowed to be used. Even if my dm allowed me to use it unmodified, I would feel like I had an unfair advantage.