Renogy 100w Bendable Solar Panels!

I'm new to solar, at least when it comes to the technical stuff, but it seems to me wattage is irrelevant. For example, 180w / 36v = 5amps; which seems to me to be the important thing to consider... amps... for charging. And one must buck the voltage down to a useful range, so isn't that extremely wasteful, or does one gain amps while bucking voltage?

Or, is needing 36v to obtain 12-16v just the nature of the beast when it comes to solar?

thanks!