Not sure what you are after, large solar is simple, small solar a bit of a trade off, the problem is a controller uses energy, so with a large panel no question a switch mode type controller well worth while, but with smaller units not so cut and dried.
In the main we need some thing to store the energy, like a battery, these have a fixed voltage, but the solar panel will produce more power at a lower voltage morning and evening than at mid day, so to get the maximum power we turn the DC to AC and transform it to what the battery needs and then turn it back to DC.
But for a small unit this uses more power than it gains, the same for turning the panels to follow the sun. So size is important.
Also selection of battery, alkaline batteries can be left part discharged for ages, in fact they are better being discharged to being fully charged, acid batteries are the reverse, they become damaged if left discharged.
So all depends on why you want solar power.