First of all, please don't scream at me for using SoftwareSerial instead of the real thing. I did it because it has better documentation.
Here's what I need help with:
Noise | Does the connection get noisy or bad with long wires?
32U4 > 328P | I'm communicating between a Micro and a Classic Nano and I'm wondering if one will kill the other or something because of differing processors. They shouldn't, right?
Communication | Is this two way? I need to send data from a couple of I2C sensors but also need to receive inputs to activate some IR LEDs and stuff.
but if you want to keep the Serial ports for uploading code and debug, sure Software Serial (with all its quirks and limitations) can do the job (but the API is very similar although won't be as robust)
Software serial is often reliable. However there are circumstances whereby incoming characters are dropped, whic can be a problem reading a GPS for instance.
NeoSWSerial does not suffer from the same problem.