I played an Iron Label fixed bridge RG with EMGs and it sustained forever. The EMGs sounded very digital, but the guitar was nice. I should’ve bought it. I figure the EMGs had a bit to do with the sustain though. None of my Edge guitars sustain much at all. Thought maybe the fixed bridge was a major part of that.
I have a basswood 540R and a basswood RG6UCS. The much older 540R rings out very nicely and is my best sounding guitar unplugged. The new RG6UCS doesn’t sound terrible unplugged, but not nearly as good as the 540R. I think basswood works well as a tonewood. Generally pretty balanced and smooth. My mahogany S1220 is also loud unplugged, but sounds like mahogany does.
I believe the locking nut and trem being metal to metal on both ends gives them all an added brightness compared to a regular nut. This gives a bit of a strange affect with the S having the low, low-mid mahogany characteristics and then a spike of brightness at the very top end.
The guitars all seem to take on a bit of their unplugged characteristics when plugged in.
Thinking about that RG521, but would like a fatter neck to add more meat. Spotted some 7 string fixed bridges used, but not too sure about a 7 string. Nice fat neck though.