I can't answer your first question; that is pure personal preference. If it were me I'd get a transacoustic

Second question - Dealing with audio on the N3x is fairly easy although you may need to teak the audio out from the Mac to get the sound you like. There are a few options here:
1) USB cable to mac for midi, mini stereo jack cable out from Mac to Aux in on the piano, disable the piano on board tone generator.
2) Midi port out to convert to connect to Mac, mini stereo jack cable out from Mac to Aux in on the piano, disable the piano on board tone generator
3) Yamaha BT Midi adapter plugged into midi jacks on the N3x, Mac receives midi data via bluetooth (using that adapter as the N3x doesn't have built in bluetooth), mini stereo jack cable out from Mac to Aux in on the piano, diable the piano on board tone generator.
Yamaha labels their C positions a bit differently than normal which can create confusion if you're not prepared - middle C for their instruction purposes is C3, the lowest C is C0; disabling the tone generator is the function button + C6 per the manual (so if you're used to middle C being C4, it would be function+c7).
I've done it before both using the the USB cable for MIDI and the Yamaha Midi Bluetooth adapter (MD-BT01) and it works fine.