The two XXF-BBB nibs were natural; on one 52 and the Soennecken. I wouldn't dream of grinding a nib so thin. Actually, I've never ground a nib (just smoothed some, and mostly removing tow-three generations in the dark of the drawer drag to 'good and smooth' the level under 'butter smooth', only a couple to 'butter smooth', I do have some slicker paper, so 'good and smooth', is smooth enough, where butter smooth can be a bit slick on slick paper.
Mostly I find vintage Euro F narrow enough for my regular use. My Degussa 'Easy Full Flex nibs which I have a few are just old European EF. That Pewado wet noodle is an F-BBB.
The other Waterman Wet Noodle is EF-BBB. or 6X.
As I said, I sweat because of my still slightly heavy hands, when I write XXF with those two nibs, EF requires thought of 'lightly'. F requires no thought when I scribble.
Do you know yesteryear-fountain-pens on eBay? They are based in Germany, I've bought few pens from them. Gotta be careful to inspect the pen (photos) but prices are reasonable.
If your hand is heavy, modern flex may help to get used to the form ... Aurora 88 Aniversario perhaps, or Aurora Optima (new with flex nib)... they are European fine, but not too fine... and flex, but not too soft...