I have a question about your various AU's:
In canon Alec is something like 10 or 11 years older than Max, but in most of your 'verses Max is much younger. What is the age difference between Alec and Max in your various stories, and why did you decide to alter the gap?
Oh that's a fun question with a slightly convoluted answer. The age difference between Alec and Max in most of my verses is about 12 to 13 years which isn't that big of a difference. However, Max is generally younger than in canon because Alec is younger than in canon. I usually write Alec as being 20-ish rather than 22-23 like he is in the series as Jace is supposed to be around 19 and that age difference doesn't make sense to me while they're still supposed to be parabatai.
With how young the nephilim start going on patrol (as evidenced with Max in the series) Alec becoming parabatai with Jace when there's a nearly four year age-gap between the two of them, just doesn't seem like it would make sense. Alec would have already been patrolling for several years by the time Jace gets his official runes, for one. Jace also wouldn't have been able to outshine him the way he's said to do in the series, for another, as they would be in different age brackets. (The child and teenage actors also looked too close in age to be nearly 4 years apart.)
As for why Max and Alec are 12-13 years apart rather than 10-11, it's a combination of me initially misremembering the age difference between them (and then getting too attached to it, to change it), and me getting influenced by my relationship with my youngest (half-)sibling. While both of our personalities are entirely different to Max and Alec, we have a similar dynamic as in the we hover somewhere between younger-and-older-sibling, and parent-and-child, and, as you might have guessed, my youngest sibling and I are 12 and a half years apart.