I sometimes run into this problem; I want to add detail in my mesh or do a bevel for example. Then it can get complicated to keep the model in Quads without adding a lot of edgeloops.
Now I am wondering if this is actually a big problem, but I couldn't find the answer so far. In this tutorial for example from Gleb Alexandrov he just bevels edges as in the included picture. This creates a huge Ngon on top of the cube, and so far I always heard you should avoid Ngons and tris. But Gleb just leaves it this way, and that does seem to be the far easier option.
So what are the consequences of an Ngon like this (or a tri if thats's the case)? Is it just reduced modelling flexibility? Or can it actually influence the render result (or performance)? Also I am trying to make a small indie game, so the models I make will be exported to Unity in the end. If there is extra things I need to consider regarding Ngons and tris in Unity I'd be very happy to know.