Anybody have any recommendations for Kicad defaults?
It's not easy trying to work out what to use, those trace calculators don't make any sense to me and the internet doesn't offer Kicad specific suggestions that I can just plug in.
I honestly don't remember what Kicad uses for default design rules, but the thing is that there's no such thing as a universal default.
Your design rules are based on several criteria. The trace width and separation rules are driven mainly by the pitch of the parts you are using on the board. Of course, these rules are also determined by your fab house's capabilities. For example, Seeed has 6 mil trace and space (0.154 mm) as their standard, you can pay more for 5/5 and 4/4. (Other houses do 3/3 and smaller, for a lot more money!)
Another consideration is voltage drop and power handling in the traces. 6/6 is fine for digital stuff from a microcontroller, but not good for driving motors or TECs. Kicad's PCB calculator can tell you the necessary trace width for given current and conductor length.
And remember, you don't need to have all traces conform to one design rule. Your digital traces can be 6/6, analog (op-amp, etc) traces can be 10/6 and power can be as wide as necessary.