Hi.
Cable size.
Could mean overall diameter or area (CSA). This was mentioned previously.
The CSA (Area) only dictates the resistance of the cable/wire, nothing else.
The insulation, proximity of other cables & maximum operating temperature dictate the maximum current during overload (Fuse type & rating important).
Reduced Voltage drop is guaranteed if CSA is increased. Volt drop is inevitable. I think a 10% reduction is noticeable on lights/lamps.
I would buy thin-wall wire/cable as it is possible to buy the same OD & have a higher CSA.
If you drive your car in salt water, single colours are available in tinned copper.
Cheers,
Iain.