Agreed that the REW forum is the most likely place to start. I found the stickies to be extremely informative. Maybe it was the questions I was asking but I hope you have better luck getting responses than I did. You might even post your question to the GR Research circle here.
Matthew Poes may be another resource to consider. His lane is acoustics but I find his insights and experience with REW / DSP to be especially helpful in the background.
Not knowing how much experience you have, my only other comment is there aren’t any short cuts with REW. FR is pretty straight forward but learning to read anything else is a real investment in time.
I can imagine that close mic will capture cone breakup/resonances and such but I wonder how large a space or how short a time range is required to eliminate the room from the waterfall/spectral displays.
If you’ve not already referred to it, I also highly recommend the REW help index linked below. The burst decay mode is new to me but is covered in the Waterfall and Spectrogram plots.
Fascinating and sometimes frustrating stuff but it’s a rabbit hole I enjoy. Good luck! Let us know what you find.
https://www.roomeqwizard.com/help.html https://www.roomeqwizard.com/help/help_en-GB/html/graph_waterfall.html