I have different chisel tips for my Xytronic station ranging from 1.x mm to 3.x mm.
IMO 2.4 mm Chisel tip is optimal for PCB work like that, about the same size as the solder pads.
Gives great contact to the joint to be soldered.
For most of the rest of the Crack build, I would recommend larger chisel, like 3.x mm