Resolution bandwidth (RBW) implementation

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This post addresses the implementation of resolution bandwidth in the
context of spectrum analysis in MATLAB.

Is my understanding correct:

In an analogue swept frequency spectrum analyzer (SA), the so-
called resolution bandwidth (RBW) is implemented as the final
intermediate frequency (IF) analogue filter. The RBW of the
measurement is varied by changing the bandwidth of the analogue
filter
whose shape is Gaussian.

In DSP-based spectrum analyzers, there is no 'final IF
(analogue)
filter' and resolution bandwidth is implemented as follows:

the measurement signal, sampled at Fs, runs continuously. A
segment of sampled data, of length L_segment, is windowed prior to
taking its complex FFT. The latter is averaged over N_segment
segments.

How does the L_segment and N_segment relate to RBW and Fs?

What form of averaging is applied (magnitude/complex)?

Thanks in advance for your answers. Please illustrate with MATLAB
code
if appropriate.