I found that (at least at audio rates) the 40106 has a fair amount of crosstalk if you use too many gates, seems most plans I found suggest not using more than 4. Either way, the two CMOS chips cost a few cents each, so build simplicity was more important here.
I think so, I made a few experiments a while ago, LEDs diffuse nicely through printed panels with this rectilinear pattern, which is the only one that yields acceptable transparency:
