doesn't really matter in that case.
pcm means the ps5 is doing the audio decoding.
bitstream means the sound bar is going to do the audio decoding.
the 'advantage' to bitstream is that there's sometimes additional audio channels in blurays' that the player can't/won't decode. in the case of the ps5, it's really not going to matter too much.
https://planethifi.com/pcm-vs-bitstream