Is 300ohms a good value for the resistors
Yes.
It would help if you got your terms right.
Voltage is across, current is through. Power is the product ( like in multiplying voltage and current ) is nether across nor through.
Or maybe a better question is, what is a good value for the individual resistors to achieve those
two goals?
You should only put the maximum rated current through an LED. Whether that is bright enough for a specific purpose is dependent on how efficient the LEDs are at converting current to light. You find that in the data sheet.