1. No quite the opposite the main problem with using a splitter is you have no control over the fans as they run at 100% speed unless you use a fan controller in which controls the power sent to fan itself but as stand will force both fans to run at 100% speed of the fan in which for alot of fans is quite loud so a fan controller is petty much essential.
2. the one issue you will have if ur using a splitter on the fans is that ur cpu fan speed will no long be automatic to the temperature of you processor raising but that shouldn't be an issue if you running them at 70% you shouldn't need any more either way.
3. Not that I know of alot of fan controllers have control over there own led's in which u can change the fan controllers led but if you want to change you fans leds with a control that would require some soldering or a case with a compatible fan controller and fans to do so.
4. I prefer to use motherboard fan pin connectors as oppose to fan controllers I only use fan controllers if I do not have enough motherboard fan connector to have control over my fan speed but this is a matter of preference.
Thank you so much! I tried to do as much research as I could but couldn't figure out everything I wanted to know. That looks like a great fan controller, I'll be going with that one since the Gelid doesn't come with red backlighting (black/red build).
Those LEPA fans look REALLY cool, but they dont move as much air as I'd like them too. It should be alright though. Thanks again, this really helped!