There's a genesis plus gx wide core for retroarch on 3ds, you can use that to mimick the widescreen, but that's the closest you'll get in terms of emulation. You'll just have to wait for the source ports to become old 3ds full-speed compatible.
There are Input Redirection cilents that make the New 3DS’s C-Stick the same as a controller’s right analog, but if the circle pad pro is something different, I have no idea.