4 tubes would work great. If you want to try and get away with two tubes,
buy a fixture with a wide reflector. Two of the two-tube shop lights on
each shelf will work good.

Generally fluorescent fixtures aren't noisy at all.

Either T12 or T8 should work fine. I think T8 fixtures often come with an
electronic ballast, which uses less electricity and puts out less heat.
Distance will depend a bit on the height of your tallest plant, but with
most Paphs the base of the plants should probably be less than a foot from
the lights. Check the output of the different bulbs, it varies widely.

I'm no expert on day length, but somewhere in the 12-16 range would probably
work. 18 seems a bit extreme if you have an adequate amount of lighting. I
think mine are around 14.

-danny