oh lordy where do we start? get a sandwhich and hunker down, this will be long.
as for sizes, if your floor area is exactly 2x2 then you may have issues because the cord comes out the side and will add about an inch to an otherwise exactly 2' long fixture... cut a small hole in the side of the tent to slip the cord through then tape it up? hmmm. and a 2'x8 fixture would be really good for seedlings, but 2-3 plants would easily fill out and occupy the whole footprint... a 4' fixture would be plenty for 4plants through flowering, but a 2' fixture is really only gonna cover a 2' area since you want to keep your bulbs as close to the tops as possible, so your footprint is limited to about the size of the fixture. Something to keep in mind.
As for the spectrum. The bulbs you were talking about (psuagro also, although I know you're familiar with PAR already) they all have Blue/Green/Yellow, for the most efficient photosynthesis you want blue/red. Those lights were developed to provide light for the human eye, which is most receptive to green wavelengths at about 555nm. plants "see" differently. They are most receptive to Blue light around 440nm and Red around 630-660. NONE of those bulbs have any red at all, they all peak at 610nm which technically is still in the orange range and is not very well used in the photosynthesis process. They ALL use a "tri-band phosphor" to create the emitted light. There are actually 3 main wavelengths (colors) of light that blend to make a white-ish light. If it is heavier in the orange range the "kelvin" temp are lower (ala 2700k and 3000k which are referred to as WARM) If the light appears "bluer" it traditionally has a higher kelvin temp, a 6500k bulb next to a 2700k bulb will appear very blue and crisp next to the warm and glowing orangish 2700k bulb. All the light you see is created by 3 colors blending though, blue/green/orange. The only useful photonic energy you're gonna get from any of these bulbs is blue (for the most part, this is the beginners class, we got a long way to go if you want advanced lol).
Now some will argue that if the bloom bulbs are mostly wasted orange/yellow light, and the plants really want Red, they why can you grow with them??!?
Yes the orange bloom bulbs will work despite their lack of actual Red. But just like with HPS which are actually a very poor providers of light for photosynthesis, you can bombard a plant with enough photons and it will get enough energy from it to thrive, but it will never reach its full potential without the kinda light it really wants. For optimal photosynthesis, your plants want what is called PAR, Photosynthetically Active Radiation. This is like the powerband for light, that is most efficiently used by chlorophyll.
Now most "tri-band fluoros" have spikes in three areas...
1. blue (which most ALL provide a pretty good spectrum in blue and cover the plants needs quite well, its hard to find a bulb that DOESNT provide a plants full dose of blue) both chlorophyll A and B have spikes in the blue range, from about 430-450nm, which most commercial bulbs are abundant in. Blue is VERY important to the plants, but there are only two bulbs I know of that dont contain blue, so you dont have to worry about it too much. You'll have plenty to provide your plants.
2. green (again, its hard to find a bulb that doesnt have a spike near 555nm green) green is not completely un-used, as its presence in a light blend can increase the efficiency that OTHER colors are processed by the chlorophyll, but it is not utilized much in the photosynthetic process itself. Not completely useless, but its hard to avoid so you dont need to worry about providing it, you'll get some no matter what.
3. orange (red...) Again its very difficult to find a bulb that doesnt have its 3rd spike in the vicinity of 610nm (phosphors that emit higher than this (630/660nm+) are very expensive and are the golden egg for growers) Plants use this 610 wavelength very poorly, just a little deeper and you get around 630nm which is technically where the reds start, and where plants start to use the light more efficiently. The peaks being at 630nm and 660nm. Bulbs with these wavelengths are gonna be more expensive due to the expensive/rarer phosphors, and they wont be used in commercial lighting because they will emit a more rosy glow with a low CRI... not good for people's sight.
So these tri-band bulbs simply adjust the levels of each peak to give its hue, bloom bulbs have alot of orange and less blue, grow/6500k bulbs have more blue and less orange. 4100k and 5000k both have lots of green which is great for us to see with and appear WHITE, but are creating light that is about as useful to plants as a skateboard is to stephen hawking
Its all about adjusting the levels of these 3 cheap phosphors to create a blend that will emit a certain "color" hue, all designed for humans.
Now for veg, red isnt as important. It will promote faster growth which includes lengthened internode length. My veg blend has a low proportion of red to blue, which causes slightly slower growth, but its very short and squatty and VERY short node distances (like 8 nodes at 3inches
I would estimate the proportions of my veg blend to be about 10blue, 5red to 1-2green.
For flowering, obviously red is more important, I think my flower blend is probably 10red, 7blue, 2green...
Ok, basically Im saying the cheapo bulbs are good for vegging, since they dont provide much red (even the blooms), but for flowering you'll need to supplement the reds somehow. AquaMedic Plant Grow, ATI ProColor, AquaticLife Roseates, ZooMed FloraSun, CoralLife Colormax all provide 630-66nm and are marketed for freshwater aquatic plants or reptiles. UVL RedSun/RedLife are the only bulbs I know that are almost pure PAR Red at 630nm, but they're hard to find now since they made a bad batch that are failing (2of my 4 crapped out in the first week) hopefully that will be fixed soon.
For Veg, you'll do fine with all 6500k's as I did when I started with all grow bulbs. I got much shorter and squattier/bushier plants (granted slightly slower growing) when I added 2of4 bulbs in pure blue (wavepoint BlueWave and ReefWave which cover 420nm-450nm/// $8ea). Im still getting short/bushy plants but a little quicker growth now that I changed those two 6500k's to FloraSuns which provide 630-660nm red instead of the 610nm provided with the generic 6500k's.
For flowering, I'd just as soon stick with all 6500k's over the blooms, they produce too much orange/yellow/green which isnt used very well. The grow bulbs will at least be giving a bigger dose of blue which is better used by chlorophyll. I would make an order now for 2 UVL RedSuns, they're about $20ea, but they're the only way to get your levels of red up enough to give a boost to the flowering process. Otherwise FloraSuns are only 8$ea and are an excellent bulb to use in flowering. WavePoint CoralWave bulbs (8$)are essentially a blue actinic bulb providing a boost of Infrared at 760nm which helps to trigger flowering.
before buying any bulbs, see if you can get a fixture that will provide actininc bulbs so you have some pure blue bulbs as well as 6500k's. Some fixtures can be ordered with your choice of bulbs, actininc/10000k for aquariums or grow/bloom.
With 4 6500k bulbs, throw in one or two WavePoint BlueWave and ReefWaves for a boost of blue during veg and you'll get much bushier plants with shorter nodes.
for flowering, swap those 4 6500k's out for FloraSuns, swap out two of the blue bulbs for RedSuns, and the other two blue bulbs for WavePoint CoralWaves which will still give the full blue plus the IR to trigger flowering.
Veg=8bulbs...
4-6 or 8 6500k's ...+
optional improvements
1-2 WavePoint BlueWave
1-2 WavePoint ReefWave
Flowering=8bulbs...
4 ZooMed FloraSuns
2 UVL RedSuns
2 WavePoint CoralWaves
Shopping List!!! (in addition to your free 6500k bulbs)
4 ZooMed FloraSuns x 8$ea
2 WavePoint CoralWave x 8$ea (Actinic +IR)
2 UVL RedSuns x 20$ea
optional improvements...
2 WavePoint BlueWave x 8$ea (replaced by the cheap actinics if you can get them with you fixture)
2 WavePoint ReefWave x 8$ea (deeper blue than the 460nm actinics)
Gimme a little time to edit this to add some pics and SPDs (spectral distribution graphs), Im super stoned and rambly and need to clean this up. Sorry if I went into stuff you already know, but bottom line, most any light will grow plants, but you want the best results you can with what you got, so you gotta do it the best you can right
Hopefully a few can learn something new from this. Check my signature for some nice pics to illustrate my ramblings better