Use Jolt: The Best Physics Engine For Godot! 

Why isn't Jolt on by default?

for the ball particle sim, jolt might just be not calculating the physics for old balls past a certain number of instances. Jolt may be optimized out of the box for certain scenarios like massive amounts of particles. The could also be using different time step functions, maybe godot's adds more energy into the system while Jolt's is tuned differently.

Is Jolt open source or do you have to buy it?

doesnt work on web😢

when I pick up a thin rigid body it can phase through the floor, I haven't had this issue with Godot's physics. is there any fix?

so the weight from above has no effect? isn't that less physics ???

Yeah? I've tried that. Unfortunately with Jolt on my character no longer go up slopes.