I know your question was for @Mike but I can tell you as someone who has a DBX286S in my chain that the expander/gate does a fantastic job of removing ambient noise.
You’re welcome @David. I found it a wonderful investment as I used to do a lot of what the DBX does when I edited in post but having that has enabled me to not only reduce time in post with recordings but also allows my radio show to sound better too as the mic is being processed in real time so the processed output is what goes out over the stream.