This is a quote from the F360 manufacturing forum seems to summarize my situation.
"Unless the 3d op toolpath is aligned with an X or Y axis, it’s going to be line segments. It’s a fundamental limitation of many controls and probably fusion."

I have a Shop Sabre model 23, 3 axis mill with WinCNC and am unhappy with the 3D cutting times. I have spoken with Shop Sabre customer support and WinCNC support several times each. After more than a dozen trials air cutting my conclusion on the machine is that Fusion 3D parallel (raster) give the smallest tool path size and shortest actual cutting time. I have tried most every 3D option and only morph spiral comes close. I have also adjusted tolerances and smoothing to reduce file size. Actually, 2D adaptive clearing is faster than 3D adaptive clearing on my machine. The 3D parallel appears to simply raster with Y (in my case) being held constant. The actual cutting time with gcode of 180 ipm is usually 80-90 ipm actual. That is 45-60% of fusion estimated machining time with file sizes of 700 kb. 2D actual cutting with gcode of 180 ipm is usually 170 ipm, 95% of the fusion ipm estimate. This is with a HSD 2.2 hp spindle. It is annoying to watch a machine this size cutting at 90 ipm.

Although the machine can rapid 300+ ipm, vortex recommendation with their tooling is 180 ipm max with the 2.2 hp spindle. No sense upgrading the spindle if the ceiling of 3D is 100 ipm.

Question – Is there logic to the controller affecting the cutting time? Are there controllers that are better at performance for 3D tool paths? It is interesting to me that none of the files cut so far have any lost steps, loss of detail or failed. The on screen running gcode steps are in sync with the machine movement and code scroll stops when the spindle rises to return home. I am not sure if the code scroll indicates the controller not “feeding” drives in real time or not.

Until a couple years ago I had access to a ShopBot PRS48 and Buddy. With those machines I was cutting 280 ipm actual. Of course, 4.5 hp, servos and 440 v. My shop now is limited to 220 single phase besides not having the space or budget for machines that size. Probably adds to my being annoyed with 90 ipm.

Steve. (apology for the dissertation, but wanted to give enough information.)