Thank you for the answer, i was thinking to the same idea but the problem is "how" remove/delete the already instances made.
Animation Nodes doesn't have a node for this.

Again thanks!

@Kimerabubble If your Object Instancer node had a count of 100 and you later turned that down to 70, it will remove the 30 objects that are not needed. So you don't need to delete them yourself, the node will do it for you. That is what I meant by:

then change the instancer count to match the new count after culling,

Yes i know but the problem is that decreasing the number of instances it deletes the last born and not the first born so I should "transfer" or shift all the actual information about transformation between the instances before decreasing the number, not so easy...

For example

t0: Instance 1 borns
t1: Instance 1 have a collision and change translation, rotation and maybe many other data in simulation
+ Instance 2 borns
t2: Instance 1 continues its simulation in RigidBodyWorld...
Instance 2 have a collision and change translation, rotation and maybe many other data in simulation
+ Instance 3 borns
t3: here if i wanted to delete the Instance 1 (the first born) i couldn't decrease the count of instances from 3 to 2 because i would delete the Instance 3.

In order to guarantee the actual collision of the instances i shoud transfer all the data
from Instance 3 to Instance 2,
from Instance 2 to Instance 1 and than decrease the count of the Object Instancer...i'm not so sure how it is easy to do and how much it could impact the performance.

I hope to have explained it well.

@Kimerabubble I think this is the only way unfortunately, because the Object Instancer keeps track of those objects, and removing them manually is possible, but it will confuse the node.

I don't think transferring the data is a bad option, but it doesn't have to be like you described. You essentially need to store the entire data in an array and operate on that array independent of the objects themselves, then set the data to the object at the end. Check this method for data storage for instance:
https://blender.stackexchange.com/questions/106679/make-particles-slip-around-objects-in-animation-nodes
https://blender.stackexchange.com/questions/105090/how-to-store-particle-locations-in-a-list/105178

Understood and thank you for the links, extremely detailed! I didn't know the possibility to transfer the entire data like that.
I'm going to learn how to apply that on instances of my context.
I will post you the result!

Thank you again!