3x MIA is useful in many situations. Concerning Twin Waves, it is perhaps not the best example because it has 2 attenuators (param 1 and param 2 knobs). That said, 3x MIA will be able to mix and dose two sources of external modulations that will result in a single flow in one of the two inputs (param 1 or param 2 inputs).
I don’t sell modules :) When I write 'We often suggest...' I am referring to this ModularGrid community (and others) that quite often recommends the 3x MIA module. It has many useful functions in a small 6HP format. https://www.modulargrid.net/e/happy-nerding-3x-mia
In fact, it is one of the highest rated modules currently (see the list of ‘Top Modules’ https://www.modulargrid.net/e/modules/evaluationlists)
It is not always relevant to advise this or that module (apart from a few utilities) because the beginner logically has a difficulty in explaining what he is looking for, and the one who advises will naturally refer to his own tastes and orientations.
Take your time. Watch videos. Download and read the manuals for more information, and understand for yourself. I did this for several months before purchasing my first modules.
And start with few modules (but a large box)...
'On ne devrait jamais quitter Montauban' (Fernand Naudin).