A question I would ask is what amp are you using? Difference between a 8 watt tube and a 500 watt ss can determine if you want to go with 14g
My advice is 12/2 (likely will not hurt your hands) and will cover all amps
RFI is everywhere (if you are on planet Earth that is lol)
If you have 6 open legs in your breaker box make sure your box is not oversized for your line into the house.