New HackPro Build Graphics question

[alecwild]

Hello! I'm a first-time Hackintosh builder. 

I'm looking to build a good video editor (FinalCut Pro X and Davinci Resolve). I shoot 2.5K raw, but not 4K (yet). I want to run dual displays.

I'd like to keep the budget at around $1500.00, give or take a little.

My thoughts on the build:

Gigabyte GA-Z97X-UD7-TH $202
Core i7-4790K - $320
Graphics Card - See question below
Crucial Ballistix Tactical (32GB) $280
Samsung 850 EVO 250GB - $100
Seagate or WD 1TB HDD x2 in RAID0 - $102.00
Corsair 650 watt - $110.00
Corsair Carbide 500R Mid Tower Case - $100
TP-link PCI Express Wifi Adapter - $37.00

Monitors, wireless keyboard, and mouse already owned.

So, several questions, and please excuse the noob-ness.

1) Should I get a 4GB graphics card, like the EVGA GTX 970? I understand from reading the forums that a card like this would be a more intensive install, since I'd need to download drivers. Or should I instead try for something like 2x GTX 760 2GB cards in SLI, and use one for the GUI and the other for GPU intensive apps? 

2) In either instance, will I need liquid cooling or extra fans, given the recommended case? (Carbide 500R) Would ACX versions of those GPUs affect this?

3) Will the thunderbolt ports work out of the box, or will I have to install Windows in order to initialize them?

4) Is there anything in this build I could downgrade/change to save some money?

Any advice you guys could give me would be greatly appreciated. I'm excited to build my first computer, but a bit nervous too!

Thanks!

[Pavo]

SLI does not work in OS X

[alecwild]

But I can use two cards on that mobo, yes? One for GUI, one for graphics apps?