Advice on clean (SPST&DPDT) wiring?

[thehops]

Hey folks. So within the next week or two I'll be looking at tackling a bit of wiring for some lights of mine. Truth be told, automotive electrical is something I'm not overly comfortable with, so here I am. Feel free to talk to me like a first grader.

My vehicle is a 2010 Nissan Titan. Here is what I am going to be working with:

-x1 40 inch DPDT amber/white bar
-x1 20 inch DPDT amber/white bar
-x2 3 inch DPDT amber/white pods (I would like these on the same switch)
-x3 10 inch SPST white bars

I would like everything to be wired as cleanly as possible. I am looking at a Blue Sea 12 circuit fuse block (to allow room for expansion), and possibly a circuit breaker if recommended. I have harnesses for each circuit (3 DPDT with relays/switch/leads, and 3 SPST).

Some of my questions:

-All of the harnesses have inline fuses and relays. Is it redundant to utilize a fuse block? Should I connect straight to the battery and organize my relays within the engine bay instead?
-What is the best method to keep this jumble of harnesses manageable?
-The harnesses have a built-in switch. Can I cut these off in order to wire in switches of my own choosing?
-Considering my 40 inch bar is 240W / 20A, is there a maximum safe length of wire I can run to the battery? The factory wiring looks to be 12AWG.
-On the DPDT lights, there are two sets of power/ground leads, one of which I'm assuming is for the switch. Is there a go-to place within the cab to connect these to?

Again I am fairly new to messing with the vehicle electrical system, so even the most basic of advice is appreciated. Thanks all!

 

[Hnoroian]

One fuse is good, two can lead to more problems (i.e. another connection to worry about) use buss bars/distribution block since they already have fuses (blue seas is great). Keep your relays in the same spot, and lable them (cover them if not waterproof)

Loom, shrink wrap, and zip ties

Crimp and shrink wrap well for your own switches. They may already be 1/4" quick connects already.

12ga does about 10-14 feet

Last one I can't help you there, too many variables to move around.

But serious about cleanliness use wire ties, some loom and shrink wrap makes it look wonderful, and quality crimper and proper connectors and ofc multistrand primary copper wire.