I've been using Rx for a while but I don't really use the Denoiser module that often. If you're trying to quiet crowd noise during quiet sections like at the beginning of a track you're better off adjusting your fade in and then using the Denoiser or Attenuation module in the Spectral Repair. The best thing for this is an adjustable envelope for this if that's included in your DAW/editing software.
The Tonal filtering adjustments are only there if you need it. Most of the time I just tick the broadband setting and if the result has tonal noise as a result of the processing, I try again with tonal noise reduction ticked. Just like the manual says, tonal noise is a watery/chirping sound that needs to be filtered out.
It's a little confusing (at least it was confusing for me). The tonal noise is the result of the noise reduction or rather it's what's left after the broadband filtering is done. If you try and remove noise that contains too much tonal/musical elements, the software will think that the tonal content is something that you don't want to remove and leave much of it behind. The trick here is to realize that stuff like chatter contains lots of tonal elements. Otherwise, we'd all sound like robots when we talk. So, when you ask Rx to remove nothing but broadband noise, it does it's best to remove just that. Quite often there's going to be some tonal elements there too and after any broadband elements are removed, all that's left sounds like chirping and watery sounds (which are the inflections we add to the words we speak to add emotion or anything else that's remotely musical).
There may be a way to use the Denoiser to remove something like the hundreds of voices of folks chatting before the music gets going but I've never had much luck with it for that sort of thing. What it's really good for is stuff like surface noise of an lp or a constant noise like an air conditioner. What I've found with live concert recordings is that it removes too darn much so the acoustics are lost and the recording sounds dead. But, like I said, I haven't really tried it enough to be certain.
I really love Rx but it has a long learning curve. I've logged a lot of hours on it and sometimes, I still feel like a total beginner.