Hi Mike,
You are correct about the tuning speed and step size.
You can find the DANL specs here,
https://relatedcontentdemo.kinsta.cloud/download/sm200a-data-sheet/
The RBW will add 10*log10(RBW) dB to the noise floor.
But, sometimes a picture can be instructive.
I attached an image of the device configured for the 1THz sweep speed. You can see the device sweeping a 20GHz span in 17.257ms with a 30kHz RBW and a reference level of -20dBm which will configure the receiver for maximum sensitivity. If you increase the reference level the noise floor will come up in 5dB steps.
Let us know if you have additional questions.
Regards,
Andrew