Prison_Mike

1. Your GPU is too hot, you need better case cooling. My 2080 TI never even hits 70C after adding adequate case fans and exhaust setup. Add more cooling so your expensive components have a chance to live a long and happy life. 86 might fry your GPU sooner rather than later. Matter of fact your GPU might be throttling. 
 
2. Since your GPU is so hot, what are your CPU temps? Is your CPU getting so hot that it's throttling too? That could be causing it.
 
3. Do you have monitoring software unknowingly bottlenecking your GPU? Precision X1 is set on my computer to restrict temperatures, but by default it was set to restrict bandwidth. If you are running monitoring software make sure it didn't somehow get set to prioritize limiting your GPU performance instead of temperatures. 
 
4. WTF with your 768P TV? Maybe your components think they are too good for their home, to quote adam sandler, and don't want to play nice at such low resolution. Just saying
 
5. What kind of benchmark scores are you getting - timespy etc? 3D mark is only $5 on steam 
 
6. Try different PCI slot like that other guy said

Noone is curious why he is running a 1360 x 768 mini TV with a PC like that?
I am.

No problem!  you can also plug all your stuff into this site, to see the absolute bare minimum that your setup will draw, this number seems to be short typically though. especially since any heavy load tasks with increase power draw.
 
PCPartPicker part list / Price breakdown by merchant Type Item Price CPU Intel - Core i9-9900K 3.6 GHz 8-Core Processor $529.99 @ Amazon CPU Cooler Antec - Mercury 360 RGB 73.31 CFM Liquid CPU Cooler   Motherboard ASRock - Z390 Taichi ATX LGA1151 Motherboard $189.99 @ Newegg Memory G.Skill - Trident Z RGB 32 GB (4 x 8 GB) DDR4-3200 Memory $289.99 @ Newegg Storage Corsair - MP510 960 GB M.2-2280 Solid State Drive $249.99 @ Corsair Video Card EVGA - GeForce RTX 2080 Ti 11 GB XC ULTRA GAMING Video Card (2-Way SLI) $1717.04 @ Amazon Video Card EVGA - GeForce RTX 2080 Ti 11 GB XC ULTRA GAMING Video Card (2-Way SLI) $1717.04 @ Amazon Case Lian-Li - PC-O11 Dynamic (White) ATX Full Tower Case   Power Supply EVGA - SuperNOVA P2 1200 W 80+ Platinum Certified Fully-Modular ATX Power Supply $179.89 @ OutletPC Case Fan Corsair - HD120 RGB 3-Pack w/Controller 54.4 CFM 120mm Fans $74.99 @ Amazon Case Fan Corsair - HD120 RGB 3-Pack w/Controller 54.4 CFM 120mm Fans $74.99 @ Amazon   Prices include shipping, taxes, rebates, and discounts     Total (before mail-in rebates) $5073.91   Mail-in rebates -$50.00   Total $5023.91   Generated by PCPartPicker 2019-01-22 17:18 EST-0500    
You can edit the parts as you see fit to make sure everything is correct.

The P2 1200W? I recommend not getting it. A single rail 1200W PSU is just silly. If you get a high wattage PSU, make sure it supports multi rail. The P2 also has complaints about not being particularly quiet. 
Check out the RMi, HXi and Dark Power Pro 11. 

Well, I'm using
I9 9900K OCed
4x8GB ram OCed
2 GTX 1080 TI OC edition with 120% power limit and 100 Mhz OC.
1 14 TB HDD
1 Optane Memory
1 950 Pro
1 1 TB HDD
6 case fan for water cooling
1 3.2W DDC pump for my custom water loop
 
When playing shadow of tomb raider the GPU usage is 100% for both GPUs and around 40% CPU usage. The average power usage is less than 700W (I'm using a TP Link outlet with build in power meter that I can see in the App, I'm not sure how accurate they are). I would say 1200W is enough. I have a 1600W Platinum tho.

A RTX 2080 ti has about the same power consumption as a GTX 1080 ti so a 850 watt PSU would be fine with SLI and no overclock.
 
 
 

I have the EVGA PSU he linked, and it is excellent.  It would be enough for your system if you are definitely not going to overclock it.  My rig has a 7820x and single 2080ti, both overclocked, and I have seen it pull 740w+...add another 2080ti and I would be seeing ~1100w.  Too close for the 1200w psu in my opinion.  If I were you, I would just get an EVGA 1600w and never have to worry about it.

Just started up The Division, took a screenshot at a peak wattage. This was in the base so not many things moving around, and I was running forward to make the wattage go up, but this will pretty much be peak.

I can tell you exactly, I have this system. Actually a fair bit better due to custom loops and screens and stuff but anyway,
 
According to Corsair Link, I use about 200W at idle.
 
CPU only load at 5.0Ghz (CPU-Z benchmark) - Around 305W peak.
 
GPU load (gaming good enough?) With SLI enabled based on The Division with 3440x1440 100Hz display at ultra: It moves around 450-700W it fluctuates. Peak I seen: Power in: 780W and power out: 800W (not overclocked), OC will increase the number by 60W on the GPUs.
 
Specs in the description.

Thats good option, Honestly though, if you are not considering pinching pennies, I would opt for something more like a 1200W PSU, especially if you think that you might ever Overclock any of it. Plus the EVGA XC will draw more power than the Zotac, 

something like this:
https://www.amazon.com/dp/B00KYK1CKI/

2080ti has factory power limit from 260w to 300w depending on the card, then the 9900k at stock can pull about 200w (depends on how much voltage the board automatically sets to). Not like the CPU will actually do that easily in a game because you're still GPU bottlenecked at 4K. I'd say you're just within capabilities of the PSU, but better undervolt the 9900k and preferably lock it at a lower frequency to reduce power draw. The GPUs can be undervolted as well.

I've found that this website gives you a general round-about idea of what you'll need (https://outervision.com/power-supply-calculator) but as @TheKDub said you'll always want to go a little higher just to give it some headroom. Plus you could always decide to overclock so getting a PSU with a higher wattage will let you do that as well.
 
Below is the approximate results of what you'll need based off of what you said you're getting.
https://outervision.com/b/3mzESS

I think I've written this elsewhere on LTT, but if not ... my system is a bit different than what you're thinking about:
1 OC'd 7900X
2 x OC'd FE 2080Ti cards
OC'd DDR4 (4GHz)
Some storage, etc.
 
With that all said, I have a 900W UPS.  Annnnnnd ... nope.  Under load, the 900W UPS says, "Nope.  Nuh uh.  No sir.  Not happening.  I can't cover this for you...." *click* and it shuts off.  Which, as you can imagine, is a bit annoying.
 
So, I doubt your 850 will be enough even without OC'ing your hardware.