Summary: 1. Rounded track matter above 3 GHz 2. Champher (45 deg) are better than 90-degrees bent, simulation shows input impedance varies by 10% span of 1-10 GHz @8:47 3. No straight forward or out of box way to create curved trace multiple workarounds available
Thanks for posting this. The one thing that keeps me on Altium, for now, is the ability to have nets assigned to arbitrary polygons. I import DXF from Microwave Office and convert to polygons, then assign nets.
If your bandwidth is so important and return loss so critical then use stripline for the small section. What I mean is glue in a small piece of substrate over the track in question. This removes the effect of differences in velocity of propagation in air (above substrate) and in the substrate. Microstrip is crude (but effective) for connecting RF signals but sometimes stripline is required, such as in couplers. Also, get a copy of ADS and see how it's done.
When i have footprint of RF design with multiple pads on the same net, the ratsnest still wants me to connect all of them. There is no way of telling kicad that these pads are already connected through the footprint.