Kinda sounds like combine infill layers in prusa/super slicer, that setting will have it do the perimeters as per normal but do infil at 1/2/3 etc layers, so 0.2 layers would get infill every 0.4 at 2, so it’ll print the perimeters and anything that can’t be merged, go to the next layer and do the perimeters and chunky infill, I use it to save time and I haven’t noticed much difference in functionality.
I found Freecad has become fairly intuitive if you already have traditional parametric cad experience, there’s definitely a few quirks but generally super easy to adapt to if you come from solidworks, inventor and the like, trying to convince my dad to give it a try as he’s been getting back into design since retiring and he’s been paying for a solid works license. Personally use ondsel but mainline freecad is totally useable.