I have a 30' extension cord I use so I can take it outside or work around any side of the car.
Unless you go a long way with small wire the voltage drop isn't an issue. No different than a wired receptical, just use a heavy duty SO wire and 30-40 amp plugs.

I like the variable voltage, much easier to get a clean weld on various metals, I can play with different settings rather than adapting to the set speed and voltage settings.
But that's why they make both kinds I guess, some like the presets.
My tank is the middle size, I forget the poundage, it'll last a long while in a back yard shop.
The smaller tank would definitely make it more portable.
Get the larger spools of wire, the small ones are a joke and .030 seems the best all around wire but get a smaller .023 spool as well.