I work in Archicad with a coloured pen set with various weights just as you seem to be doing.
However also have a 'black/grey' pen set that has all the same pen weights but the pens are various shades of black, grey & white to my choosing.
For example I decide if a yellow pen is going to be black, grey or white.
Then in the layouts I set all the drawings to use the 'black/grey' pen set rather than the default colour pen set.
And I set the 'Colours' option to be 'Defined by Pen Set'.
I set my Publisher up to save as PDF files and in the PDF options I leave it set to print as 'Colour', but of course because they are black/grey pens, they will print exactly as they are.
At no time do I let Archicad or the PDF converter translate a colour pen to grey scale.
At any time in Archicad I can switch to the 'black/grey' pen set to see what it looks like on screen.
It may not help with the display of the pen thickness - you may still have to zoom in/out to register the different weight lines.
Unless you are zoomed in close enough, a thick line will look the same as a thin line.
It may be more prevalent on a 4K monitor - I don't know as I don't have one.
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Versions 6.5 to 25
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