How to improve the modelling quality of that area in the piece?
Looks like you need more bevel weight in the enclosed “triangle”… see my example for clarity.
This is a tricky piece… my approach was to keep everything connected and as low-poly as possible (just focusing on the lower part in question and starting with a 16-vert circle):
…only used edge-loops where absolutely necessary (just the lower transition area in this case) and relied on Bevel modifier with weight limiting and Miter Outer type of arc followed by subdivision surface modifier to add curvature. The blue edges above is where I want “edge” so that is where the bevel weight goes.
Not having any n-gons and minimal triangles helps.
@zeroskilz, thank you very much! Your illustrations helped me a lot!