Dude does his homework. This I like.
I'll work through the questions that I can answer:

1) I read a book that said the CFM for the fan should be 3 times the cu. ft. of the room so it exhausts the volume 3 times a minute!! What? mistake?
You want to vent at least every 5 minutes. 3 minutes is a bit much but I'm sure there are conditions that call for it. Adds crazy CFMs to your requirements though.

2) What is the affect on airflow for a 90 degree turn in a duct? I was thinking for the ceiling vent I would need this to run the fan and filter across the ceiling.
Take you base CFM (HxWxL / 5) and * 1.5 for each elbow. * 1.3 for the carbon scrubber.

3) If I use a rectangular horizontal reflector, then I should put the long sides parallel with the short sizes of the room (28") correct? This limits which reflector I get, and the ones with built in duct ports wouldn't work. Therefore I was thinking of the Hydrofarm Radiant Reflector.
I'm not sure I follow. I'm thinking you would want the long sides parallel with the length of the room so as to cover as much area as possible. No?

4) Wattage... I am torn between 250W and 400W. At first I will grow what I can old school organic, nutes, and soil in pots, but eventually I want to learn ScrOG. 250 W should do 2x2 feet max I'm told, but with 400W I can maybe get a wider area in that room, but is it overkill, or is the space too small for it? I like the power savings with 200W, but I hate for my plants to not get what they need.
It is overkill. Your space is not deep enough. However, if you are going to want to cover a 4ft wide area at some point then you will want the bigger light.

You can do the ScrOG from the get go. You are doing your homework. Why not? It only adds a little more complexity but not much. Just keep on doing what you are doing.

5) One book said a minimum of TWO oscillating fans is required, really?
I like one stationary fan under my canopy (especially for a scrog) and the one oscillating fan on the canopy. You only need two if you have a large enough area to justify. You only need one.

6) Venting straight into an insulated attic okay?
I assume that it has a ridge vent to dissipate hot are and moisture. If so you're good to go.

7) If my exhaust fan is on a timer or environmental control unit, what is the affect on plants during the time when it is off, in other words, don't they need lots of fresh air (CO2) all the time? It seems bad to ever not run the exhaust fan.
If you are not adding CO2 then I would run it all the time. Others with more knowledge on this may have other thoughts.

8) The intake will be to the adjoining closet (through false wall), is this bad? the closet isn't air tight or anything...
Not ideal. Fresh air would be better. But any air is better than no air. It will be fine.

9) I live in a coastal area, the temps are moderate, I plan to make my night from NOON-6pm, sound good?
Yup. Nothing wrong with that.

10) Equipment, can you say if the Active Air 4" inline fan (165 CFM) is quiet and long lasting, or should I get the 4" Vortex? What do you think of Phresh or Phat filters vs. Charcoal Filter Elf (coconut)? What do you think of the Hydrofarm Radiant reflector vs the Sun System 2? Bulbs? Agrosun Gold Halide, Sunmaster Warm Delux? Ballast, Sun System Cropmaster switchable 400W, or maybe Lumatek 250W/400W switchable/dimmable electronic?
I'm going to let someone else cover the lights. If noise is a concern then you want to research carefully. I'm guessing it is as it will be in your room. For starters, you can locate the fan in the attic which will mitigate a lot of the noise. Have a look at Panasonic Whisperline Fans (see westsidesupply.com for good prices. I have not used Fresh or Phat filters. Phat used to go by a different name until recently. They sure are priced right. I'm using Mountain Air which are a bit on the price side but they are supposed to last 2x as long.

Good luck. You are heading down the right path.
bigsby Reviewed by bigsby on . Read a lot, made a plan, but have questions (noob). Hi! I think I might be decent at this indoor gardening, and I started reading the sticky, the noobs guide. I also have been reading a couple of books. My plan is to convert an existing bedroom closet with limited depth. It is actually a very wide double closet, but I am going to use half of it (for now). The half I will use is about 78x28x95 (width, depth, height) inches, so the volume is about 120 cubic feet. I will vent to the attic, and attach a filter, using Rhizome's noob guide, 80 CFM Rating: 5