Buffer Size

Buffer size should not affect the bounce. Are you bouncing Real Time or Off Line. Use Off Line.

Unselect Normalize in the Bounce dialog. Posting a screenshot of the Bounce dialog here could help us to better help you.

Why are you playing the buffer size? 1024 is ok when mixing and bouncing.

WD

There's something else wrong somewhere. The buffer size helps the CPU to cope with varying amounts of information. The more tracks/plugs/synths the harder the CPU has to work and the more raising the buffer setting will help with this although the higher it is, the more latency you get.

It does not affect the audio quality at all. It will either play back glitch free or with glitches (if the buffer is too low) at the audio quality your project is set at and it won't dynamically reduce it if it is struggling. Logic just doesn't work like that. So something else is wrong somewhere.