Hi, If enough connectors, use the motherboard headers (for controlling their speed depending on the temperatures).
Connected to the power supply, they would permanently run at full speed.
Yes but try to connect them all on the same cable line. Don't connect fans to the same cable as the video card (if there are extra cables on that line) nor to the hdd. You could use the cd/dvd cable line but make sure that the CD/dvd drive is tha last on on that line.