Confirmed that “retain on load” combined with priming the SoundBase (UGameplayStatics::PrimeSound) before playing results in no delay on packaged builds in 5.3.1.
Until now, I was using the “force inline” load behavior, which seemed to be working with no problems on my environment, but I think I’ll switch to “retain on load” since other people in this thread were reporting audio bugs when using “force inline” - although I wasn’t able to confirm such bugs myself.
Edit: Although there doesn’t seem to be any noticeable difference in audio quality/behavior between “Force Inline” and “Retain on Load + PrimeSound()”, I measured a ~20% overall slower loading time when all sound data is set to “Retain on Load” compared to if it is set to “Force Inline”, for the first time when entering gameplay in PIE in-editor. So I’m switching back to Force Inline to speed up the initial load after starting up the editor.