I usually use speakers, but Razer Synapse 4 changes my default audio device every time I turn it on.
My microphone is often changed to the headset microphone, but my main microphone is actually the Razer Seiren Mini. Since it doesn't support Razer Synapse, it doesn't get set as the default microphone on startup. This means that Razer Synapse 4 not only changes the default audio device on startup, but it also only changes to devices supported by Razer Synapse 4.
Additionally, the device changes made by Razer Synapse 4 seem completely random. My headset has two modes: Game mode and Chat mode. Sometimes it changes to the low-quality Chat mode, and other times to the Game mode. And these are just two options. If I were to buy more Razer audio devices, it would be disaster upon disaster. Imagine the chaos of having Synapse randomly choose a default device among three or more options every time I start my computer.