I am not sure about the 'traditional' Topaz plugins. I have never tried but which of those can work with RAW files? I tried it with Adjust 5 but Adjust 5 cannot display RAW files.
You can send a RAW file form CO to Topaz Studio and back to CO without any problem. (see attached). I am on Windows but it also should work on Mac (I hope).
right click on the thumbnail of the image you want to send to TS and click on 'edit with'. Choose Topaz Studio from the list, choose file format and resolution and click ok. Make adjustments in Studio and the click on Save. this will send the file back to Capture One.