Best practices on splitting 12 V 20 amp supply into 5 devices?
LEDs are subject to thermal runaway.  You can google "LED thermal runaway" to find out about that, but long story short they need some form of current control. 

At any rate, assuming all of your devices are acceptable for the voltage range they will experience, you can connect them all to the voltage supply.  However:

Each conductor supplying power to a device must be rated for the maximum current it is expected to draw, the highest temperature it will experience and the highest voltage it will sustain.  For a 6A LED, a 6.4-7A fuse should be fine, and a wire rated for 6A.  You can go to larger sizes of wire to reduce volt drop and increase efficiency, but if you do so, you should still size the fuse based on the load.  Cheap inline automotive fuse holders are ubiquitous.  Make sure the components you use are rated for use in your area (for Canada you want Canadian Standards Association(CSA) or Underwriter's Labs(UL) approval) if your vehicle counts as a vehicle.

Each time conductor size is reduced, the smaller conductor should be protected by an overcurrent device(fuse should be fine) to protect from shorts without having to shut down the whole system.  Each fuse should be set as low as practicable, meaning it should have the smallest possible current value without ever tripping during normal operation.  Your PSU has 60A overcurrent protection(or if not you should add it), which won't do anything to protect a 5A load or a 10A wire.

For splitting the output of that converter, you can run a wire capable of 60A to a bus bar.  A bus bar is basically a block of conductor with screws for the purpose of tap connections.  Use inline fuseholders on each smaller conductor that taps off the bar.  You may be able to use an automotive fusebox as well, but keep the fuses accessible and as close as possible to the source.