Hello!
Ed isn’t using any fuzz on Myxomatosis. The fuzzy sound is actually they lead synth that Jonny plays and which is likely sampled for his midi keyboard for live performances. On both the album and during live performances, Ed is just using some overdrive. It’s a little faint, but certainly audible (shifted a little to the right) on the recording. From 2002 to 2009 he used his Crowther Hotcake, and in 2011 he switched to using his Carl Martin AC-Tone. If you listen to the From The Basement performance, his overdriven guitar is easily discernible.
For the live version of Codex, near the end of the song Ed strums the same chords that Thom plays. He may also do it elsewhere. If you listen to when everyone is warming up at the beginning of the From The Basement performance, you can clearly hear him strumming the chords, and you can also watch him strum them near the climax of the song. It’s dark sounding, so perhaps he’s strumming with his thumb, though he could also have turned down his tone knob. In addition, he adds some sounds of fingers moving on the strings, which can be heard near the start of the song. I assume that this is deliberate, since he likely would have muted his guitar otherwise.
It’s possible that he also does this very sublty on the album version, but I don’t hear it.
I’m not sure if he really is as underrated as many believe, which a surmise from tons of comments about him being the most underrated. Perhaps he is underrated by the average fan, but the most underrated? I don’t know if he takes that ~throne~ from The Graf.