There will be variations in quality and the amount of light produced depending on the vendor of the LED. The answer to your second question depends on a. The length and brightness of led bars required, b. The circuit configuration. c. Where the transformer/ power supply will be located. It needs to be located in an accessible location. d. What sort of transformer/ Power supply - dimmable, magnetic or electronic? The following discussion contains quite a bit of info with respect to low voltage LED http://ths.gardenweb.com/forums/load/lighting/msg0600194417283.html Depending on your needs, direct wired 120V LED UCL may be easier to install. The Philips power cove LED light bars are good. I looked at the LED bars Lowes and decided not to use them - not cost effective. The color (as I recall) is about 3000k.

Use an ELV dimmer. I'm using the Lutron Diva (DVELV-300P-WH 300-Watt Diva Electronic Low Voltage Single Pole Dimmer) with eW powerCore MX lights (higher output LED lights intended for cove lighting)

WAC is a very good brand. What I have is something used in the sign industry. It is a similar tape that they run inside the large plastic letters for businesses so that the letters are lit. I had a choice of warm or cool bulbs. I can't tell from the WAC site if you have that choice or not. Of course, I didn't like either...cool was too blue and warm was very yellow. So, I bought some of each and alternated the bulbs for a balanced color. Electrician thought I was crazy.

I didn’t do led tape but in my laundry I installed this low profile under cabinet light and really like it. They can be linked together. They are hardwired but you can also order a plug for $10. There’s an on-off switch but I put mine in a wall switch. Also you can direct the light on the unit. And there’s a set here to change from 2700 to 3000 depending on your need and preference. The piece that I’m touching tilts so you can direct the light. The problem I’ve seen with tape light without a shroud is seeing the reflection from the individual diodes. I am going to install WAC tape for above my bathroom cabinets but they are so expensive. I’m still looking for a lower priced option for my shoe cabinet in closet. Too large of a run for the WAC $ Good luck!