If I remember correctly the line weights in sketchup/layout are a combination of the sketchup style settings and the layout style line weight setting, where the former is multiplied by the latter.
So for example,
Your sketchup scene has a default style with the following edge settings: normal edges = 1 (the default minimum), profile lines = 2, and section cut widths = 3.
Place the scene on a sheet in layout and apply a line weight to the viewport style. Lets say 0.5pt.
Layout will then multiply the sketchup style line settings by the layout line weight setting to arrive at a final displayed line weight for each element.
So in this example layout will output the following lineweights:
normal edges = 0.5pt, profile edges = 1pt and section edges = 1.5pt.
If you are tricky you can use this functionality to stack viewports for a wide variety of lightweights in your drawing however there is a trade off in time and performance so you need to find a level that works for you.
Line types (dashed etc) are more of a problem. For lines that are unlikely to change such as boundary lines etc, I tend to draw them in sketchup, output a “dashed lines” scene to layout, place the viewport and explode it. Not the best way in terms of sketchup links but it is quick.
Hope this helps.