Wwise Integration 2021.1.1.7601.2102
Checking Unity game's FPS via the Unity Stats window (recent Unity versions display accurate FPS values)
After I upgraded Wwise to 2021.1.1, if I enable Unity's "Enter Play Mode Options" and disable the "Reload Domain" option, when I enter Play Mode the Unity game noticeably starts stuttering, and the FPS will drop, compared to when Reload Domain is enabled.
Even worse, each time I exit and enter Play Mode again, the game will stutter and the FPS will drop even more.
I guess some static fields or static event handlers from Wwise 2021 aren't being properly cleared when Domain Reload is disabled. Then, they keep accumulating in each Play Mode and thus making the FPS drop more and more.
Unity reference for supporting "disabled Domain Reload":
This issue doesn't happen if "Reload Domain" is enabled, or if the "Enter Play Mode Options" are disabled.
But I'd expect for Wwise 2021 to be compatible even when Reload Domain is disabled, because this setting is a huge timesaver for lots of Unity users, and Wwise 2019 didn't suffer from this issue (see below).
Before upgrading Wwise to 2021.1.1, I used Wwise 2019.2.9.7459.
In this older version, the FPS bug doesn't happen. The Unity project still maintains its original FPS and doesn't stutter, even if "Reload Domain" is disabled.