Well, made another test sample and got some interesting insights.
Test specimen I: 1mm (based on standard settings, outer wall thickness 0.35 and inner wall thickness 0.3 ---> 0.35 + 0.3 + 0.35 = 1mm)
Is printed exactly how I wanted.
Test specimen 2: 1.23, because the default settings state a wall thickness of 1.23, consisting of 4 walls.
Does print without an infill as well, just prints the lines, so this is also fine!
Notable difference, specimen I ---> first print the outer walls, then the inner wall
Specimen II --> first prints two inner walls, then the outer walls. Probably because it tries to squeeze 4 times a 0.35mm line into 1.23mm.
Anyone who could give me insights on the line width of 0.35mm with a nozzle of 0.4mm. Sounds very counterintuitive to me, would expect it to be 0.48mm like most other printers/software. Does it have something to do with the 'air gap'? Would like to know how Cura deals with this, as I am looking for an 'ideal' minimum wall thickness for optimal strength and dimensional accuracy.=