Best to start/end segments/arcs at the exact coordinates.
I'd first try to set a rough grid spacing.. like 1mm or 0.5 mm and draw a simple rectangular outline and go from there.. deleting/adding single segments/arcs as I go to keep it consistent, if you do your outlines in KiCAD (*)
*) alternatively you can draw up an outline in a CAD program of your choice that is able to export DXF, as the ability of KiCAD to do arbitrary arcs where start/end points meet other arcs/segments is very cumbersome. CAD programs have that one down as their main function
Naturally with simple 90deg arcs/segments you'd be faster in KiCAD still.