a dimmer isnt required but can be useful
leds are more efficient and dont draw the heat that bulbs would draw
less heat means you can get the lights closer, run them harder and have less active cooling
you also have cct/color options for having more control over what type of light the plants are receiving and when
you wont really get the par and UV you would from say, a CMH but some led monos will give you a good boost in par
you dont have to use a tent, its just more convenient for some.
a driver is the mostly the same as your ballast used for your cmh/hps/mh etc
however, i do believe that this is causing brighter environments for our plants and its increasing their need for certain nutrients, magnesium being one.
just some info in my folders
Univ.Utah_Growlight_spectral_characteristics.pdf (1.3 MB)
rapidled has a good selection
solstrips from @Baudelaire are also a very good option. hes that guy that can hook you up with what you need