I feel your pain. Conexant drivers and application are frustratingly difficult to remove from my system and I have the same problem where they come back once removed. And the Conexant app itself cannot even be uninstalled once the drivers are removed. You can click uninstall under apps and it does it thing, but nothing actually gets removed and the Conexant app is still listed under the apps. And then the next time you reboot it just reinstalls the Conexant drivers, which have a soft and tinny sound compared to the MS HD Audio drivers. INCREDIBLY FRUSTRATING to say the least, and your term "take over" describing the hideous Conexant software and drivers is spot on.
It seems like MS is pushing the Conextant drivers and software out to peoples machines which is surprising given how buggy they are and the fact that they were found to have key loggers in them in the not too distant path.
I'm running Windows 10 64-bit. How can I get the Conexant off from my PC and keep it off, as simply uninstalling it isn't working.