uhh, yeah, I'm with you on that. never seen/heard about a difference in dufus/doofus. Both get the red squiggly line of misspelling
However, I'm firmly of the opinion that "newb" is friendly while "n00b" is not. My brother would argue, but I've seen an increase in the use of "newbie" to refer to a novice.
Recently I heard an audiobook narrator pronouncing "demur" like "demure", which tells me it's a pair most folks don't know