solo vs pool mining

Hey,

i know that you need a lot of hashing power because of the difficulty to be successfull on solo mining. Sure thats one of the main reasons for pool mining. But what i'm asking myself, does the pool software also split the work to all the clients to be more efficient ?

Something like - miner 1 hashes on range 1-4000 , miner 2 hashes on range 4001 - 8000 and so on. Not sure if this is even possible or makes sense.

But lets say someone has enough power for solo mining.
.) Simply let all rigs solo mine on there local ethereum blockchain ?
.) Point all rigs to a local Proxy which holds the chain ?
.) Build your own Pool with pool software and point all your rigs to this private pool ?

Whats more efficient ?

Thanks !

regards