Hai Dilipfeb,
Welcome to the forum. The output current needs are better defined by the user who wants to use it. And if you are the end customer, your specification should be
a. output voltage and % tolerance and noise limits.
b. output load current with % variation.
c. input voltage (minimum and maximum) for delivering the required output.
d. Niose limits (switch noise should not be fed back to the input supply.)
e. Size of equipment
f. The max temperature which the system can tolerate while delivering the needed load current. This should include the method of ventilation like forced ventilation or only convection cooling only.
g. Protection and grounding needs.
Please google for power supply specs for buck boost converters for more details, etc.,
After this you may start considering the component selection, whether purely discrete, partly discrete with ICs taking control, Microprocessor / microcontroller based, Frequency of operation for the load and size requirements ... then go further.
All the best