A dual power supply if usually very much like two more or less separate supplys, that can be connected in series and sometimes also in parallel. Series connection is usually easy, parallel connection needs additional load sharing parts and is thus more complicated.
With so much power, you likely want to use at least two transformer taps, to reduce the power dissipation.
I would prefere the layout with a foating regulator, like many old HP supplies have used. This needs an additional auxialry supply for the regulator itself, but is very flexible (same board could be used for 10 V 5 A or 50 V 1 A - just change a few resistors and the transformer).
Just for learning, a smaller supply (e.g. 2 A only) will not change much, but parts get cheaper, not as heavy and cooling gets much easies. For so much power one would usually consider a switched mode supply that is much harder to build and a little more noisy.