Reply To: Regarding the triangle
Insetting that area doesn’t get rid of the triangle:
But the thing with all quads is important with subdivision surface modelling and there you can use triangles sometimes.
Simply said; a Triangle stops an Edgeloop and a Pole ( a Vertex with more or less than 4 Edges connected to it) re-directs an Edgeloop.
Do look into the ‘Fundamentals of Modeling’ course by @jlampel .