The rig behaves similarly to a regular rigify rig. That is because it is based on one and then modified to include very helpful bonus features.

I encourage you to move, rotate and scale all the different controllers, to see for yourself how it affects the model.
All the different functions are too numerous to list at the moment, so I encourage exploration. The names of the controllers are usually a good hint for what the function is.
If you take a look at the n-panel transform when having a controller selected, you can see which channels are locked. Those will not have an effect on the model.

The rigify UI script "Legacy Generated Rig Refined_ui.py" is present and lets you control many of the things you know from regular rigify rigs. You can access it in the n-panel.

I have created a UI script "Picti Legacy Rig UI.py" for a few of my own functions as well. You can access it in the n-panel as well under "Legacy Rig - Picti Properties".

The rig is compatible with the Wiggle Bone addon (https://blenderartists.org/t/wiggle-bones-a-jiggle-bone-implementation-for-2-8/1154726)
To make use of it, select the rig, and in the object properties, set the "jiggle_enable" custom property to 1.
Then every body part that was set up with wiggle support will wiggle, as long as the scene also has wiggle turned on.
From here it's easiest to use my n-panel menu to turn on and off different parts to your liking. You can control if the part should wiggle at all, or how much, how stiff it should be, etc.

On certain body parts you can change the behavior and controls between Tail and Spline. Here too, my n-panel menu will come in handy, as you can simply adjust the slider to your liking to blend between them. Some of these body parts are usually the tail and ears.

If you want to scale the model up or down, I would do the global scaling on the rig object itself. You can use the root bone for small adjustments, but I found that the corrective smoothing is causing undesired effects when the model is too big or too small when scaled by the root bone.

All facial expressions are driven by bones, with the shapekeys just being there to correct the shape. They are automatically activated when the control bones are moved, so you don't need to worry about enabling them manually.