I do strips for my driveway arches. I do 2 16ft strips. I zip tie them to the PVC and haven't ever had any trouble. Just zip tie it at the cut points not on the light or any of the electronics. For ease of connecting I have each arch connected up to its own outlet out of a pixlite 16... I will...
I use a DC Brushless Micro Blower. I mount the mini blower in the case with the small end pointing down and just made a small cut at the bottom of the box and it forces air out and doesn't take up much room.
I have run two power supplies in parallel and it did work but I did see some gliching. This was just a day or two of testing but when it is easy to power inject correctly, I see no reason to make this part of your permanent setup. Besides I did see so issues with effects especially in fading.
Dream color is a branding name... don't worry too much about that. Just concentrate on what the controller drives (like 2811 or 6803) and how many pixels it will drive.
The amplifier is basically taking the signal that you setup for that particular set of pixels and multiplying buy the number...