At this point i think i would go for a 5700 if you want AMD... Anyways look if you monitor is g-sync compatible and maybe you can pair it with an nvidia with confidence.
Yeah the Vega 56's are looking like they're going to be sold off at a nice price level now at least for gaming utilization with the 5700 and 5700 XT are reaching near or above Vega 64 levels closing in on the VII even though costs can vary, retail pricing here seems to be around 500 US Dollar (Or 450 Euro.) for the 5700 XT (And then shipping costs.) with the Vega 56 at a similar level and 64 a bit above but many stores seem to be discounting these down an additional 50 - 100 USD from a quick price conversion from Swedish to US currency. 1920x1080@120 should be doable for Vega (CPU limitation might be a bit of a bigger factor however.) and with FreeSync a dip below 120 FPS shouldn't be too problematic so I suppose it hinges on pricing but yeah if the monitor is part of NVIDIA's adaptive sync compatibility list that also opens up for comparison with these GPU models now that they're working with this and adding more models almost every driver release though the requirements are pretty stringent from what I know. Even at that resolution the 5700 probably still holds a bit of a edge over Vega though for what AMD has but availability and pricing plus the used market if you have a reputable source or seller for the hardware, might see a large increase in cards from users upgrading or sidegrading to these and the XT version as well. EDIT: Hmm but for the moment the Navi's are all using a blower type fan which makes a bit more noise and has a bit of a limit on how well it can cool the card down even if it does vent out the hot air so that is also a thing if you're not going to be waiting a few more weeks for non-reference models first and what these might bring in terms of cooling and other changes to the PCB. (Driver maturity as well but a few weeks might not be a huge change here.)
I don't think Nvidia does VESA adaptive sync over HDMI. That's why the OP said AMD is the only choice.
I've found a cheap Vega 56 Pulse with Vega 64 Bios flashed in it (It has samsung memory) Now i have a GTX 970 G1 but is not being enough for 1080p High/Ultra.
Hmm that's a tough one, you get a Vega 64 bios flashed Vega 56 if you take that GPU so higher clocked memory but is it entirely stable and what was the bios used in the flash, this is both a performance benefit but also a complication particularly if it's a Hynix memory Vega 56 as these have other characteristics compared to Samsung as the memory type. A boost in voltage and clock speeds for memory around 945 - 1000 Mhz instead of 800 is a nice bump though but I don't know if I would chance unless I had flashed and tested the card myself although I am fairly cautious and a bit too worried perhaps about what can go wrong but that's not a bad card potentially and would offset the weaker memory clock speeds on Vega 56 which is one of the limiting factors on this GPU potentially giving a free 5 - 6% performance bump when it performs at peak. EDIT: I would definitively consider it though but I don't want to hasten you to just buy it either and it's a good thing to be aware that bios flashing can be risky and have drawbacks so stability versus performance and potential degradation down the line possibly though not guaranteed. (HBM2 for all it's advantages is sensitive.) EDIT: Right so degradation generally sees the user having to lower the HBM2 clock speeds if overclocked which can occur months or over a year from flashing or pushing the clock speeds higher than the hardware could support which generally either has crashes or a corrupt (Green lines.) display image so from 1050Mhz to 1020Mhz for example but I could find no definitive answer as to what causes it and how frequent it is and how long it takes for it to occur and other causes but it's a thing for overclocks including bios flashing, Samsung memory supports up to 1 Ghz and even without a flash 900 - 950 Mhz can be doable whereas Hynix has different properties and some don't overclock well at all or others can reach close to 950 or a bit above 900 Mhz although every GPU is going to vary slightly. Just to have it mentioned, also one reason why a flashed card is a bit of a double edge or how it's called with benefits and potential drawbacks but maybe not immediately or it could never happen at all and continue to be stable until replaced. It's important to mention it so I tried to describe it but I am not very skilled on the subject either though my own Vega 56 Pulse at stock bios with Hynix memory but a 900 Mhz clock speed has been stable for over a year now though it's not Samsung and there are differences between the two and also between Vega 56 and Vega 64 memory timings so it's not just speed and voltage. Not to discourage but just for awareness and again every GPU is going to be a bit different. Overclocking and bios flashing is a risk after all though the advantages are nice. (Vega 64 liquid cooled bios however has a reduced thermal limit at 75 degrees where it shuts off so I'd be vary of that one unless the card has water cooling on it that can keep within this temperature limit.)
Got it But i'll undervolt her a little bit A Vega 56/64Bios is a little overkill in 1080p so i think then i'll be fine