When to multiclass abberant mind sorcerer

I have a level 12 fallen aasimar abberant mind sorcerer and I plan to multiclass into divination wizard 2. Hear me out, I rolled very decent stats, so I put one of my juiced rolls in intelligence to go along with my mind flayer tadpole roleplay. I currently have 8 str / 14 dex / 17 con / 16 int / 15 wis / 20 cha. The party consists of a bard, cleric, barbarian, and a rogue. I feel like with my current stats, the divination wizard 2 dip could rival a straight level 20 sorcerer. What sold me on div 2 was

1) Spell slots. Specifically warlock 2 entices me almost as much but at level 20 you’d be missing a 6th/7th level spell slot which is pretty big.

2) Portent is portent. Obviously very good, and flavors very well with the mind flayer mind control ideas.

3) Optimizing spells known as sorcerer. As a sorcerer, it’s very hard learning more then one or two high leveled spells for each spell level. With wizard 2, you can take all of your level 1 sorcerer spells as a wizard. On sorcerer level ups, swap them out to eventually have no known 1st level spells but extra high leveled spells known. I really like this cause 9th level psychic scream looks like it’s for my guy but how can one not take wish?

So the real question is, when should I go for it? Going sorcerer 18 first then div 2 would be the obvious answer from a power gaining standpoint, but if I wanted to optimize the spells as described above, I’d be swapping my level 1 spells out with nothing to replace them with until wizard 1. But the sooner I take wizard levels, the slower the spells known progression is. Since my spellslots would still scale as a full caster I would cast disintegrate or counterspell/dispel magic in the higher slots until I actually learned 7th/8th/9th level spells. But abberant mind 14 also looks so juicy.