Light Bar/Accessories wiring

Was wondering if people with a little electrical knowledge might be able to tell me if there is anything wrong with my plan or if there is something I need to add.

I just bought a light bar but instead of using the harness that it comes with it to wire it up i've decided to make mine own wiring setup that allows for more accessories in the future. I've seen similar ones on these forms. Attached is a little wiring diagram that I tried to draw up.

I am still not sure what gauge wire to run though, I find different answers all over the internet. The harness it comes with is 16 awg, the heavy duty harness is 12 awg, and some calculators online say I should run 10 awg. any advice there? wiring for both the Light bar and the illuminated switch.

Fuses? if the light bar draws 180w / 12 volts = 15 amps. so would I use a 15 amp fuse or should I use a 20 amp fuse?

Thanks for the help.