Yeah, the pixelation is a symptom of a disso being active and DXM exhibits it even more. The thing of not recognizing yourself in the mirror is special to DXM imho, never got it with other dissos but on plateau 3 of dxm I just saw a weird meat creature staring at me. Was indeed weird.
And DXM is indeed not the best cough suppressant, I think opioids are better. I, too, discovered the lower plateaus while dosing higher and higher due to a cough and suddenly stuff began to be euphoric, specially music and movement.
But it seems like there is a wide variety of how individuals react to DXM or to dissociatives in general, some like me find them profoundly euphoric and addictive while others, maybe even the majority, doesn't. I think I'm specially prone to dissociatives because my natural state is very attached with anxiety, recurring thoughts, dysphoria etc , the opposite of what dissos induce for me. But I over-/abused them and had to quit for quite a while. I'm tempted to buy some DXM but my gf doesn't want me to...
I remember seeing serotonergic like fractals but with more pronounced violet back in my teens when I discovered the drug but then I got put on SSRI and should never get visuals again.