Depends on the food. For vegetable soup I just toss the cubes in with everything else but for cream soups I make the cubes into stock separately. I've never tried adding them to non-soup dishes directly because they're very concentrated and I'm not certain their seasoning would distribute properly, depending on the dish.
Basically anything that's watery-ish is fine because it will boil and separate the particles evenly (particles move easier through water than almost any liquid besides some special chemicals iirc) but cream soup is much thicker and has taken up a lot of the potential for free-moving particulate.
Same goes for anything else. If you can see the water move and behave like water, it should boil and disperse the cubes. Anything that behaves thicker than water risks the cubes not dispersing properly so you risk unexpected salty bites.
In both cases though I'd stir enough for it to disperse. I do expect it to need some more stirring for thicker or creamy soups, but I don't see why there's should be a difference. I even just plop a few cubes into a Bolognesesauce, stir well and let it simmer
The issue is that success may be different from uset to user. I do indeed just put the cube straight in and have no issues with whatever i make. Even to add flavour to rice! But my standards may be lower than average