AC/DC converter followed by DC/DC converters
Reverse engineering a great design is far better than trying just to use formulae. Try an old PC PSU with a 5V preload.
You need both skills, but measuring every signal to small  &amp; large step-loads and with flyback, is the best way to compare.      - use a 50 Ohm AC coupled load from coax to attenuate probe noise is the best way and use a CPU heatsink with fan and a 100W controllable FET for current steps is a good start for an active load.
Examine the RsLC:Rp Bode plot with simulation such as http://www.Falstad.com/afilter and see how removing the load affects. then try to model the slope and phase lead feedback using the ideal Op Amps to quickly model the result. ( some learning curve)
when I used to conduct DVT’s in the 80’s on PSU’s and HDD’s I would use my design skills to reverse engineer each product and compare the timing and window margins for every type of disturbance from heat, shock &amp; vibe  to altitude, crosstalk, EMI susceptibility and much more to understand where the weakness was in each design from Fujitsu, Shindengen, Toshiba, and Seagate, Maxtor,Miniscribe and 20 other competitors.
It’s the best way to learn from others great designs and mistakes.