CSR8675 programming guide w software and tons of CSR info

Something with just aac?
Nope, nothing. Neither QCC nor CSR chips support AAC encoding, it's actually the same as with LDAC and actually quite a bit worse. At least there are some LDAC transmitters, but AAC ones don't exist (yet?).

Bluetooth isn't a DIY-friendly space, most of the off-the-shelf boards are totally locked down, others just don't do what you need them to and you'll have to spend months fighting with them.