This is something that I’m afraid you need to check it yourself. There are two types of optimization, CPU and GPU. GPU is related to rendering stuff while CPU includes both rendering and technical tasks. This means, if it’s related to hard references, it might have to do with CPU saving data into the RAM. It’s not particularly bad cause your OS will handle most of it. But again, I’m just guessing here, I have no idea what exactly it is. You will have to do the debugging/optimization yourself.
It’s easier to debug GPU than CPU. You will need to identify which one uses the most m/s. It can be ticks, it can be materials, it can be instances, it can be anything. To know what exactly it is, you will have to debug it.