In my experiments with transmitting realtime audio signals using Opus, 10ms frame sizes are acceptable for 1-way synchronicity (e.g. if you want the user to perform an action and hear the result as simultaneous with the action) but it's definitely the upper bound. From what I remember my signal processing professor say, the threshold to try and hit is 7ms total latency for truly undetectable processing, but I can't find a reference for that, so take it with a grain of salt.
[0] https://www.opus-codec.org/docs/html_api/group__opusencoder....
Robert H. Jack, Tony Stockman, and Andrew McPherson. 2016. Effect of latency on performer interaction and subjective quality assessment of a digital musical instrument. In Proceedings of the Audio Mostly 2016 (AM '16). Association for Computing Machinery, New York, NY, USA, 116–123. DOI: https://doi.org/10.1145/2986416.2986428
https://scholar.google.com/scholar?cluster=13472622195552899...