It’s a common problem with vector based drawing programs like sketchup and fusion360. You can’t really draw circles. You can increase the segment count to make the thing look more like a circle. In sketchup you do it by highlighting the circle and hitting control and + at the same time. You’re supposed to be able to type in the number of segments, but I haven’t been able to make that work. I’ve no idea how to do it in fusion360 - might have to google it.
You aren’t going to be able to make a true circle in either program, but you can get it close enough that you shouldn’t be able to tell. To make it “as good as possible” on the MOAI you’d use 5,000 segments on a 10cm circumference circle. That would make each segment 20um which is the finest MOAI can print I believe. I’m sure it would appear to be a perfect circle well before you got to that many segments though.
At normal zoom, a 10cm circle with only 100 segments looks more like a circle than a bunch of lines to my eyes.