Check your alternator's bearing. When mine started going south, it became quite noisy. I checked it by removing the serpentine belt and moving the pulley with my hand. It felt like there was gravel in it. Engine was much quieter after installing the new alternator.
Also, the newer fan clutches do make a great deal of noise (some describe it as sounding like a jet engine) when the engine is first started and during the first several minutes of operation. That is normal. However, still check your alternator.
Regarding the "...big V drop..." when you roll your rear windows down, a couple of things. One, check the the body ground from the battery. Follow the small black wire from the negative battery terminal to the body/frame and remove the bolt, then clean the area and the wiring terminal so both are clean and shiny. Then reinstall the wire and the bolt. Two, make sure the battery terminal to battery connections are clean and shiny. Three, make sure your battery terminal bolts are tight - not gorilla tight, but human tight. If you have a battery that's more then a couple of years old, get it tested to make sure it has not developed a bad cell - a load test is preferred over a conductivity test, but if you can only get a conductivity test, OK.
No need to replace the camshaft position sensor unless it throws a code.
If you had a window switch shorting out, it would blow a fuse or pop a circuit breaker. If after you have checked the battery out and the grounds out, if the rear windows still cause a large voltage drop when operated, then consider replacing the window regulator and motor assembly. I do know that when they get old and "worn out", they slow down and can pull a heck of a lot of current. I've had to replace all of them in both our 99 Buick Century and 99 Silverado in the last year or so. Made a big difference!