1) We will add "Opacity" slider in Perpective settings in new beta
2) 
3) how can we reproduce that?
1) Awesome! But I definitely think a “line thickness” slider will also be needed, to make it more visible when zooming out. Unless you can find a way to generally make the lines more visible on big canvas sizes. So I think that means, basically finding a way to keep the thickness of the perspective lines consistent, independently of what canvas size, resolution, grid density, etc… you choose. Then only an opacity slider would be enough (like in Adobe Fresco).
2) It’s hard to explain, but you can see on the image that they are not spaced evenly as they should be, the lines continually move close together towards the center.
3) I’m not sure, it was always there for me, doesn’t matter how many perspective points are used or in which color, but the “glitching” seems to be more apparent on larger canvas sizes, on smaller ones the horizon line mostly looks just black, mixed with the other colors of the perspective lines. I think maybe that artifacts happen because at the horizon, several lines are on top of each other. It would be ideal if the horizon line would just take one color/ line instead of overlaying multiple ones (like neutral dark grey maybe, but not 50% as that color is often used for the canvas background color. Or maybe just take the same color of the 1 perspective point, but as a slightly thicker line), and maybe that would fix it.
