Not a complete answer, but here's some more info.
Brightness
While there are ways to calculate this that aren't that complicated, it requires knowing many coefficients that are not readily available, so ends up being an educated guess at best. You can do just as well totaling your current lighting's lumen output, then adjusting for changes in fixture styles. (I consider even a simple LED strip a "fixture" for the sake of this discussion) It's a starting point. If you use proper task lighting, there's a lot of room for variance in total levels.
Uneven light
You do not want to see the actual LED elements, it's really annoying. Besides diffusers, indirect lighting techniques work well, though require more lumens due to losses through reflection.
Positioning
I'm not sure what the issue is with parallel surfaces. The efficiency is mostly inherent in the fixture's ability to direct light where it's needed. The mounting surface has little to do with this, you need to direct the light where it's needed.
White Light
The "whiteness" is measured in degrees Kelvin. The temperature a black body must be heated to emit the same color of light. Standard daylight is often taken to be 6500K, anywhere in the 5000-7000 range is close enough for most tasks. You eyes adapt quickly to small variances. In residential settings, daylight is considered too harsh because we are so accustomed to incandescent lighting, so most home lighting is produced to output more in the 2000-3000K range to mimic the orange incandescent lighting.
Noise
How audible the noise is varies by manufacture and environment, as well as personal temperament. I don't think noise data is readily available. Testing in a noisy store will not yield any useful data, other than if you can hear it from a few feet away it is too loud. Noise can be attenuated by placing it in an enclosure, but keep in mind power supplies generate heat that has to be removed by ventilation, you cannot seal it into a sound proof box.
Try to place power supplies as far from your pillow as possible, trying to sleep is when it will be most bothersome. Placing it lower so there is likely to be more furnishings obstructing a direct path will help, as well as being surrounded by soft materials that do not reflect sound as well.
What watt power transformer should I be using?
You can use a power supply like the one pictured, rated for the amount of LED's you will be driving. Read the specs on the lighting. They should tell you how many watts per a given length of the strip. So if it says, for example, that needs about 1 watt per meter, then a 15-foot section would require a 5 watt power supply. Take your total length of 76 feet, and divide by the strip's requirements. It wouldn't surprise me if you ended up somewhere in the ballpark of 20 to 30 watts.
Can I run 14 gauge wire directly from a circuit 15 amp breaker to the transformer?
No. You can't put the power supply inside the wall, and you can't bring the wire out of the wall without going through a junction box. The best way to do this is to put a cord on that power supply, and plug it into an existing outlet. There is no need whatsoever to add a new circuit or connect these directly to a circuit breaker.
Can I plug in all 5 circuits of LED strips on top of each other to the output of the transformer?
Yes, you can wire multiple strings in parallel at the power supply. If the sections are short, you can also wire them end-to-end. Double-check the specs for maximum length of a single run.
Is this the recommended way of doing what I'm trying to accomplish?
The recommended way is to plug into an existing outlet. If your lighting requirements added up to 1000 watts, you'd want a new circuit. At 20, 30 or 50 watts, it is ridiculously small in household circuit requirements.
I would also like to add a on/off switch, do they make a wall switch for 12v?
Any switch can be used for 12v. I would put the switch before the power supply. Put a cord on the power supply like this cord with switch.
Can low volt wires come right out of the wall, or do they need a junction box before being connected to the LED strip lights?
The low voltage wires don't need a junction box, but they do need a junction plate, like those used for phone jacks.
Best Answer
It's hard to advise without knowing more about what other lighting will be in those areas and the type of activities you will have going on in the larger room. LED strip lights are great for kitchen task lighting under the cabinets. Personally, I prefer LED over traditional halogen in that situation because they produce less (almost no) heat, more even light distribution, and of course, lower energy usage. Putting them on a dimmer also allows an evening night-light in the kitchen, providing just a very dim glow when you are stumbling to the fridge. Here is a video that shows the differences in the various LED strip lighting. LED Strip differences - Epoxy vs Silicon, 5050 SMD vs 3528 SMD
SMD 3528 is a single chip and SMD 5050 has three chips sometimes known as “Tri-Chip”. SMD 5050 chips are generally three times brighter than SMD 3528 chips. Also, 5050 is widely used when the application for the LED strip requires multi color (RGB). For example, each 3528 emits approximately 7 lumens per chip and 5050 emits 14 lumens per chip.
SMD 3528 LED Flexible Strips
Its dimension is 3.5mm * 2.8mm, power watts is 0.08W per LED chip
These lights are great for single color splashing of walls for both interior and exterior applications, accent lighting for plants, pictures, LED under cabinet lighting, bars and many more. 3528 LEDs can be most cost effective, but will not be as bright. However, SMD 3528 LED Strip lighting will also emit the light more evenly as these LED chips are arranged closer together on the circuit board than SMD 5050 LED chips.
SMD 5050 LED Flexible Strips
Its 5.0mm * 5.0mm, power watts is 0.24w per LED chip
5050 LED chips have 3 LED chips in one housing (Sometimes called tri-chips), and are a lot brighter than 3528 LED chips. They are used when you need high illumination for your project area. Theoretically, SMD 5050 LEDs can offer a light output of approximately 3 times that of the 3528 strips, and therefore 5050 LED chips are perfect for lighting up areas that may be subject to high levels of ambient light
Even though 5050 LED’s produce more heat than 3528, it is still drastically lower than other light sources such as halogen and even fluorescent lamps. 5050 LED’s are different from the 3528 LEDs in that 5050 can combine the three different chips to create millions of color variations which is why they are widely used in RGB LED Strip Lighting. As mentioned previously, 3528 SMD led strips come in single colors only.
Source
Edit to add my personal summary to your comment: