Hi Tom,
I did not use iso curves.
I projected a datum line onto the surface and used the vertical edge as the other datum.
Taking dimensions shown on photo I swept circles and used the pipe produced to cut surface.
The cut edge is used to sweep and cut the next edge and so on.
These cut edges are converted to curves by copying to clipboard and pasting back to become the grid.
You can boolean union the cut surface or take a copy before cutting.
I produced grid lines in the 'Y' as a check but this was not needed in this case as array along curve by
distance seemed ok.
Cheers
Barry

Edit: Forgot your 2 question.
No its not the ArrayGem option.
It's the array along curve which as a align to surface button and an option to space by distance.