Standard AAF is the default, and that matters here
The default output is standard AAF. One optional setting, the Audio Channel Combiner, groups a clip's channels into a stereo track and is not part of the AAF standard — it is off unless you ask for it, so what you deliver opens the same way in every application that reads AAF.
The one non-standard setting groups channels into a stereo track. Leave it off for Nuendo and Cubase: one channel per track is what reads cleanly, and it is what the default already does.
Roles become tracks
Every Final Cut role and subrole arrives as its own track, in the order you choose, named the way you name it. Overlapping clips within a role spill onto extra tracks so Nuendo never meets two clips fighting for one lane, and clips joined by a crossfade stay together.
You arrange the track list, rename anything, and drop the tracks you do not need before converting — and an excluded track is audio that is never even decoded, so it costs nothing.
Fades, automation and clip gain arrive in place
Volume keyframes become automation, clip gain rides on the clip, and pan travels. Fades can be written as clip fades or as automation. Crossfades, J-cuts and L-cuts land where the sound actually played, not where the picture was cut.
One file, or a folder
A self-contained AAF with the audio inside it is the simplest thing to open in a fresh Nuendo project. A referenced delivery is a folder holding the AAF and the conformed WAVs beside it, which writes faster and takes less space. Sample rate follows your source or is set to 44.1, 48, 96 or 192 kHz.