You wouldn't need a small fillet. You could do short tangents. But practically speaking, you'll get the same result as having one. Also, if you're transitioning from one side slope to another, it could be difficult or impossible to manage that transition with a deflection like that.
I'd use a radius of something like 0.5-1 foot. No deep logic there; it's just a reasonable number.
You'll also need to use a stroking length which will be determined by the radius. You'd probably want to do something like 0.04 feet for a radius of 0.5 feet, in case you want 10 intervals over a 90-degree transition. More generally, for about 10 intervals, use the radius divided by 13, which approximates (radius/intervals)*(pi/4).
I'd use a radius of something like 0.5-1 foot. No deep logic there; it's just a reasonable number.
You'll also need to use a stroking length which will be determined by the radius. You'd probably want to do something like 0.04 feet for a radius of 0.5 feet, in case you want 10 intervals over a 90-degree transition. More generally, for about 10 intervals, use the radius divided by 13, which approximates (radius/intervals)*(pi/4).