You earn less when delegating to an overbidding low fee validator than you can earn with a validator who uses all his available voting power participating in committee even if its fee higher than 0%.
This is not tech explanation on how EPoS works and benefits delegators. The tech one was done by @rongjian in The Definitive Guide to Harmony Open Staking. But there’s one important thing, I want to point you to when reading the post, that everyONE delegator should clearly understand if he wants to get maximum from his delegation - Do not delegate to an overbidding validator!
How to recognise the overbidding validator?
The Overbidding validator is a validator that has a Bid higher than Effective stake + 15%. In this case everything higher than effective stake doesn’t participate in the committee and as a result doesn’t earn.
Here’s a quote explaining my words in tech manner:
“Each BLS key in the committee has a certain voting power proportional to the share of its effective stake among the whole committee . For example, if the sum of the effective stake of all the keys in the committee is 10k ONE, a BLS key with effective stake of 1000 ONE will have voting power 0.1 (or 10%).”