Re: C8 & Cuo5 differences?
C8's are warm, high output, lots of mids, firm low end; like an 'alnico meets ceramic' sound. Very versatile in many guitars, woods, and genres.
UO C5's (the 'Blueman Signature Custom') is more vintage sounding. Moderate output, lots of dynamics, full mids, more of an 'A5 meets A2' sound. It's warmer than a C8, and more responsive, more organic, chewier, smokier, looser, more 'sag'. To me, it's much more 'PAF on steriods' than a C5. If you like a bright, sharp, twangy bridge PU, this isn't it.
For blues, classic rock, & jazz players that want a warm, earthy tone, try an UO C5. A C8 will do these, without quite as much 'character', and also do heavier rock and metal.