@Halycon Styxland
The reason why I said at most 4th level spells is because you could go Wiz 7 / Barb (or Fighter or Monk) 5, thus giving you 4th level spells. Of note this remains true even if you do go Eldritch Knight, since Wiz 6 / EK 6 gives 8th level casting (6 from Wiz, 2 from EK) as does Wiz 7 / EK 5 (7 from Wiz, 1 from EK) since EK, as well as Arcane Trickster if for some reason you were going for that, gives 1/3 of its levels, rounded down, towards your total spellcaster level for spell slot purposes.
The same is also true of deciding the breakpoint for Paladin or Ranger fwiw, Wiz 7 / Pally 5 or Wiz 6 / Pally 6 are both 9th level spellcasters for spell slot purposes, which is why 6/6 is better for the cutoff since Pally 6 is so very good.
Also of note, your Int (and Cha or Wis or whatever other secondary spellcasting attributes you may pick up) only really matters in terms of the number of spells prepared, which is only relevant in terms of your in-combat flexibility, and in terms of your save DCs. Since most of your slots are unlikely to be used on things with save DCs, it's not *super* relevant, and if you do go for control spells to improve the efficacy of your undead, armor and effects that boost your spell save DC apply universally, making it generally more worthwhile to pursue those vs boosting Int or Cha or whatever. I agree with Halycon Styxland in that I'd go for more feats over ASIs for this build, even though there aren't any real "must haves" there's lots of good options.
