Hi telnoi - there isn't any way to treat fillets themselves in a special way different than any other surface.

Generally the way to reduce their polygon count will be the same as reducing for any surface - the primary way is to move the angle slider to the left a bit so that a rougher angle is used to dice up curved areas. This has a big effect on fillets since they are tightly curved.

If your fillets are very small, then the "Avoid smaller than" could potentially be useful for reducing them - you can put in a distance value there and any polygons smaller than that length will switch to a rougher 35 degree refinement angle while other larger polygons get the regular angle value. There were some bugs with "Avoid smaller than" in v1 that are fixed in the v2 beta.

- Michael