I have some updates that may or may not be helpfull to other people.
So, at first i was testing on editor and PC, fps was fine, was around 300 when i had 2k notes. I was using box colliders and rigidbodies with isKinematic ticked on every note, moving them every frame as i needed to get from point A to point B, until i tested it on android, i used my old Galaxy Tab 3 sm-210(Dual Core 1.2Gh and 1GB ram), 10 fps if i was lucky.
I obviously was'nt happy with the results, rhythm games are supposed to run smooth so you dont have a problem with sync and other stuff. I decided to do my own logic to check if the notes were in the right position to register a hit, i tried it with the action Find closest attached to the keys and checking every frame (the ones in the bottom part of the screen), the result was better, around 30~36fps. But still not good.
Then i had the idea to make the notes static with colliders (static colliders barely affect perfomance), and make the keys and board move, that way i only had to move 5 rigidbodies instead of 2k. The result was awesome, its running 60~65 fps and the number of notes does'nt matter.
More updates to come.
Rafael.