I was wondering if its necessary to plug in the fan to the mobo as well as the molex connector to the PSU? I was wanting to connect only to the mobo to help with cable management in my case but I'm not sure if it makes a big difference.
More aboutquestion hooking case
Directly to motherboard and you do not need to connect to the PSU.
If your motherboard has a 3 Pin fan connector, then go ahead. If it doesn't you'll have to plug it by Molex to 3 Pin adapter but the fan will always run at 100%.