I don't think you even need to go to hypothesized quantum stuff. A single biological neuron in isolation is a surprisingly complex system that resembles a small artificial neural net more than an artificial neuron in many ways. On top of an entire feedback system from diffusion of neurotransmitters which doesn't cleanly map to ANNs.

Trying to estimate equivalent "parameter size" of the brain when we only superficially understand behavior of individual neurons let alone how intelligence emerges from the connectome seems too speculative to be a particularly useful metric.