I'm not sure what you mean by "at scale" but Ethereum's PoS currently has over $6 billion staked with over 100,000 validators, without any sort of delegation. T

I'm not sure what you mean by "at scale" but Ethereum's PoS currently has over $6 billion staked with over 100,000 validators, without any sort of delegation. The protocol is designed to handle a lot more validators without modification, and resource requirements on validators today are low.