Something like this
2.2 amp 12v regulatorThe one amp version will work for the 18 watt fixture
But the 18" tube , 30 watt fixture will need either the 2.2 amp version
Or two of the 1 amp version l.p.
One for each strip
Technically two strips 10 watts would be 800 milliamps at 12.5v, but at 14+ volts from converter or solar etc..The difference will be absorbed by the regulator, 1 amp 12 volt is 12 watts
The heavier version regulator is a safety, to keep the regulator from over heating, built in a safety margin and not worry about it
We off grid most of the time, ,so nighttime and lights are quiet time for us, no generator no solar, strictly battery power 12+ volts
I'm going to add the regulators but they are not a big worry for me