I would think Structural Elements would be the best option in ACA.
There are some advanced tricks to using them that might be helpful for you.
ie. you can draw a many segment polyline and apply a steel I column and get a fully mitred portal frame. You can change the widths top to bottom of those segments.
But it does take some knowledge to get there.
Also AMEP is not much more cost and has tools for those as well. AMEP is ACA+
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