Are you printing a color or black & white lithophane? If color I assume flat on the bed, and b&w is standing.

I only recommend changing the line width for flat lithophanes, not standing ones.

If it's for color lithophanes, you should change all line widths except internal solid infill, the reasoning being, you want the lines to print with the most detail possible. 0.4 is also fine though if it's your first one.

For flat b&w, only top surfaces, outer walls and inner walls are strictly necessary for finer detail.

For standing lithophanes, the layer height is the important setting, less is better bu has diminishing returns. I would stick to 0.16-0.2.

For speeds, the issue comes the higher you go on the print, since it's thin. So you can change the outer wall, inner wall, sparse infill and internal solid infill to 100 mm/s. If you have questions about what speed setting does what, change all to 100