Using Particle Filter block in simulink

Hi!

Looking through simulink example in particle filter block and would like to clarify several things:

1) when we estimate transfer function parameters below - is plant output equal to state space model measurement? if no, when is measurement function defined? in likelihood function?

$$ y[k] = \frac{20q^{-1}}{1-0.7q^{-1}} u[k] + e[k] $$

%

% Here $y[k]$ is the plant output, $u[k]$ is the plant input, $e[k]$ is the

% measurement noise, $q^{-1}$ is the time-delay operator so that

% $q^{-1}u[k]=u[t-1]$.

2) how many inputs can be in u? are they equal to state space X or to some parameters?

3) is particle filter block working for other functions and not only for the example?

4) in addition, is there a good tutorial on using filters (including particle filter) in Simulink ?

P.S. Example was taken from https://www.mathworks.com/help/control/examples/parameter-and-state-estimation-in-simulink-using-particle-filter-block.html