Hi Warren, you're welcome!

> Random question : Are the bolded lines important in terms of how easily one will be able to work with
> the mesh? Like, should I be trying to hide those behind other geometry when possible or anything like
> that? Or are they purely decorative?

Well, they're not exactly decorative - they're a normal part of the NURBS geometry. The way NURBS objects work is you have a bunch of surfaces and those surfaces have "trimming boundaries" on them that define which areas of the surface are active and which part of the surface are holes or cut away portions.

When you do boolean operations the actual "underlying surfaces" stay the same and only new trimming boundaries are created that then trim away more parts of the surface area.

Those bolded lines are the edges of your model, the edges are what make up the trimming boundaries.

It's a pretty different geometry system than a polygon mesh object, with a polygon mesh your object is made up of all little facet elements and there isn't this same concept of a bigger "underlying surface" and "trimming boundaries".

So it's not like you necessarily want to get rid of those, it's normal for your objects to be made up of various trimmed surfaces.

- Michael

You can also use some external free monster for capricious fillets in Moi like Fusion 360! ;)
And come back to Moi! ;)
(you can renew after the end of each year! ;)
https://knowledge.autodesk.com/support/fusion-360/troubleshooting/caas/sfdcarticles/sfdcarticles/How-to-get-a-Fusion-360-Enthusiast-license.html

Why not use a Variable Fillet for keep the original "sharp edge" before the last Fillet? ;)
Of course here you must make that in 2 passes due the little angle of some edges as shown above posts!



Don't press Done after the first Fillet(s) here 25° before make the Variable Fillet(s) of 0° of the 2 points on the right of the yellow "curve line"!
You can make and erase any number of different Variable Fillet(s) on the same curve(s) first selected as long as you are not exit of the Fillet function!

Variable Fillets are a little tricky but with a little training that is very easy and powerful! :)



Here a general last Fillet of 5° for example!


And careful for the second Point of the Variable Fillet of the Back faces of your ob!ject!
Maybe a zoom must be made because you have very near closed points!!!
So the Variable Fillet (s) or normal Fillet will be not work on the bad point!