Well, for kicks, I opened mine up this afternoon, and I'm impressed by how similar the 20 is to the USA version. I'm going to share them - as you'll see, nearly identical layout to the 100, which PRS shared a gut shot of in one of their release videos, so it's not like this stuff isn't already out there (plus, anyone really wants to know that bad, they'll just buy the amp).
Here's the 100, then the 20.
I can't speak to what the quality of the components is, clearly different parts in make between the 20 and 100, but that's about it. If end user experience is any indication, the interactive parts have been flawless, and that the amp has a very low noise floor, and sounds very good. The board is also quite thick, no flexing when replacing tubes, etc. The pots and power switch are board mounted on the 20, vs chassis mounted and hand wired to the board on the 100. And, just in general, the lead dress on the wiring of the 100 appears tidier, although again, user experience being any indication, very quiet amp regardless.
Pretty cool to see how similar they are.