I ran a couple of test and I noticed that StepUp reduces the quality of the copper features in comparison to fcad_kicad (maybe for speed, it definitely runs faster)
fcad running “makeCoppers”
fcad running “make(copper_thickness=0.035, board_thickness=1.53, combo=False)”
StepUp using “AddTracks”
07:20:47 FreeCAD build date: 2021/03/11
07:20:47 STEP UseAppPart available
07:20:52 kicad_parser_version 1.1.7
07:20:52 FC Version 019-24276
07:20:52 tracks version: 1.1
07:20:56 py3
07:20:56 kicad_parser_version 1.1.7
07:37:40 KiCadStepUpWB.Activated(v 10.2.1)