quick update here, I was able to solve this issue: I installed pipewire and removed pulseaudio. With pipewire version 0.3.27 mSBC codec is supported in the HSP/HFP mode, which has pretty decent audio quality that can be used simultanously with the microphone.
A more general comment: I really encourage everyone to give pipewire a try. it’s really easy to install, you just have to install manjaro-pipewire package, which takes care of everything, including removing pulseaudio. pulseaudio development appears to have slowed down to a crawl. it looks like pipewire is the future.