Voltage is an easy one for the US' it's usually 277 (commercial) or 120 (residential or special applications such as under cabinet lighting in a kitchenette). You can get some 12V as well but that is not as common. Efficiency really depends on the manufacturer. About 4-5 years ago the industry started pushing to go away from how much power is consumed per light/lamp and go more towards how many Lumens you get out of a fixture. You can get a fixture that sounds great using only 9 Watts but you may only get 500 Lumens, where as a fixture using 15 Watts giving 1500 Lumens would be far superior in terms of how much light output you are getting. http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/led_energy_efficiency.pdf As far as types of lamps and their use here is a decent article. https://www.americanlightingassoc.com/Lighting-Fundamentals/Light-Sources-Light-Bulbs.aspx I felt these gave a good overview on color temps on exactly how it looks: http://www.westinghouselighting.com/color-temperature.aspx http://www.seesmartled.com/kb/choosing_color_temperature/ Just a side note, with LED's if you live in a moderate or cool climate you really should consider going with LED as the cost has dropped tremendously. LED's love colder temperatures and will far outperform any other light. You can use LED in warmer climates but for outdoor lighting the LED will not last the same as a warmer climate (cannot really tell you cost savings but you will get some still using LED, its just the lamp may last 15,000 hours instead of 20,000). Another thing to look at is what the rating is for an LED. LED's never burn out, they will just reduce thier light output. When a manufacturer lists the rating ie L70 for 20,000 hours that means at 20,000 hours you will be getting approximately 70% of your lumens as it was originally putting out. Another side note LED's in commercial design will be even more prevalent once more buildings start getting designed toward LEED V4.0 due to their daylight harvesting/dimming requirements. Hopefully this was helpful. If you have any other questions please feel free to ask.