so how does cast on crit work with multiple spells now?

obviously, half second delay, but can it cast two spells rapidly in a row still, or does it have the wait the whole 500 MS before it can cast another.

Take for example the scenario that I crit 2 enemies.
I have idk, fireball and ethereal knives on my cast on crit.
Do I cast both of them, fireball on the first crit, and ethereal on the second?

Each of the spells linked with cast on crit have seperate 500ms cooldowns.

So, yes, you will cast fireball on the first crit, and EK on the second. Assuming your fireball is linked first.