I'm unable to make a post in User Forum for some reason, so I'm adding this here, apologies for the incorrect categories but I cannot seem to make any post.

As topic. I've worked with geometries similar to this previously as these are simply imported from DXF/DWG into a curve. However, in previous times I've used fillet on extruded objects, I am usually able to get a pretty decent and visually accurate fillet width before the geometry doesn't allow it (physically). Here are 2 examples, first one was the decent one, 2nd one is the maximum size fillet I can make (very very small):

https://imgur.com/8IX6zi4
https://imgur.com/7rkv3b4