the wattage in the psu is not all,depend the quality of the unit,that make the difference in most scenario . out here there are many "1000 w" units that have very bad reputation , i suggest to focus on a psu with the suggested watt for your system but a good quality one ( reliable brand + gold certification minimum ) .
years ago in one of my build i had a fx 9590 (220 w of TDP ! ) + 2x 980 ti sli ( very big request in terms of power wattage ) , i running it with a platinum 850w Seasonic with no one problem . another thing to consider is that the suggested wattage is overstimated mainly because is many poor psu in the market .

Granted with the graphics card recommending 750w it takes in to account only the basic PC components: motherboard, CPU, RAM, 2 – 3 fans, 1 – 2 hard drives. But my PC's always go that little bit over. After doing the math 950w should have been enough, giving an extra 50w wiggle room. (I hate mats, so my calculations could be a little off) so a 1.2Kw should give an extra 250w wiggle room and a little bit more of a boost for any future upgrades.

It's because of the amount of stuff in the PC.

If I stuck a 650 in there it would burn out within 1 min of the PC running. The graphics card alone is recommending a 750w. It currently has a 1000w in the PC and keeps turning it's self off when I use any video editing software. At first I suspected Windows 10, because of the automatic shut down that is built into Windows 10, but having bypassed that horrible feature. I've only had a similar type of problem once and that was a PSU overheating. It has happened a couple of times when the PSU was hot to the touch, but lately it happens when it is not. (It's probably already too damaged) I had a look with an Amp/Wattage meter while editing and rendering a video and the PSU tries to take in more than it is rated for, then it kills all power to the PC and restarts.

why you need a 1200 psu ? a good quality 650 w psu for the currents build is more than enough .