Hello,
I'm also using Poweramp on a Zenfone 10 with the Bose earbuds QC ultra, and same issue. Even though I would not call this a stutter but more an "audio pause" of almost half a second (happens after each/any focus change of Poweramp).
I've tried many tweaks in Poweramp but it's always the same.
Regarding the buffer size, setting it to "huge" preset, there is no difference: the pause remains, and of seemingly equal length