I too uses fountain pen exclusively and like you have a variety of them.
MB pens are nice and lovely to use but I think they are overpriced.
Pelikan and GVFC are the another brands which I love.
Love your sketches and writing - excellent penmanship.
The line shown on your sketches and writing seems like medium than fine.
I guess the paper is a factor.
Look forward to more of your inputs on pens.
/W72