What's gonna deliver more power?

 

2 4 ga. in parallel would be equal to a 2 ga wire - go with the 0 ga wire!

 

Depends on the power rating of the particular wire/brand. Most 4awg are rated ~120-130A of current, most 1/0awg are rated 250-300A of current. It also depends on how long the runs of wire are going to be.

Just run 0awg to the back then use a distro block to deliver powr to your amps individually.