My bad, I always go back and forth editing.
So, I managed to get some screenshots. First, apologies for the severe bloom. It's annoying, but it doesn't really change the scanlines' effect, so I left the images untouched.
On with the pics:
This is Line2x optimized for 320p (Japanese Sonic on a Japanese MD2), horizontal scanlines at 87%, 50% hybrid. No shimmering of course, all is perfect.
Pan:
https://i.imgur.com/hooGftg.jpg
Zoom:
https://i.imgur.com/FmdjnbB.jpg
These other two are from the same game, only in Line3x, generic 4:3, custom scanlines (subline1 87%, subcolumn1 87%), hybrid 50%.
Pan:
https://i.imgur.com/KAGhdZH.jpg
Zoom:
https://i.imgur.com/mj2dZ3s.jpg
This is where I get shimmering during horizontal scrolling in some games. It looks perfect - with no uneven patterns on still images - but the vertical subcolumn definitely clashes with my monitor's scaling: if I turn it down, to 0 the waving artifact completely disappears, and it doesn't even show up with the same settings + horizontal scanlines.
This last one is from Line5x, 1920x1080, generic 4:3, custom scanlines (subline1 and 5 87%, subcolumn1 87%), hybrid 50%.
Zoom:
https://i.imgur.com/7Gwketv.jpg
Aside from top and bottom chops, everything is perfect, I guess thanks to the 1:1 rendering, with no shimmering and/or uneven patterns.
PS - I checked whether or not there was anything I could do with my monitor's settings, in order to reduce/get rid of the shimmering (overdrive, different aspect ratios...), but nope, no luck unfortunately.