I decided that I needed to switch to a different (larger) 3D object so that my printer could accelerate up to full speed on some long straightaways. Here is what 300 mm/sec printing looks like on a larger square object:

However, my extruder just couldn’t keep the plastic flowing (at least, not at 185 C), and it jammed. So I have decided to try 275 mm/sec with the temp set to 200 C (lading to an actual extruder temp that is closer to 195 C).