If the service is decent enough with servers close by, it really isn't bad at all. In a PCgamer test, the input latency for Metro Exodus and Destiny 2 went from 46ms and 51ms local to 96ms and 75ms from GeForce Now, and 179ms and 129ms from Stadia.
For comparison, back when Tekken 7 was released on the PS4, it had 120ms of input lag.
It's should to be close enough, the spec is called sensitivity (SPL) and most headphone manufacturers try to hit around 100dB/mW.
Hopefully the setting would allow you to fine tune it based on what headphones you have.