Hi
I have had a Vega 64 Saphire Nitro + & I currently have an ASUS RTX 2070.
The Vega is a tempramental card whilst the 2070 is a plug & play card
Vega 56 & 64 are largely misunderstood in the general PC gaming community & get a bad rep (most of it justifiably so). I can tell you that both Vega cards are capable of crazy overclocking & performance when you put in the time, effort & mod them. They are some crazy cards but take a great deal of tweaking to unleash their full power & of course modding them increases power consumption & the truth is I honestly dont know the long term effects of running modded cards to their limits. Drivers have improved drastically & in general a Vega 64 performs very close to a 2070 & beats it in multiple games. When the Vega is modded I dont see a 2070 beating it to be honest - maybe in some highly optimised Nvidia titles, but in general the 64 has more power. (Requires time to tweak & mod it).
On the other hand the 2070 is actually a great card despite all the negativity surrounding ratracing. As a 2070 owner I can tell you that raytracing shouldnt be a reason buying this card right now & instead it should be based off pure performance in standard 1440p gaming. The 2070 is a good card if you plan on taking it out the box, applying simple overclocks & start gaming. The only real problem I have with the 2070 is the fact that Nvidia are launching a 2060 at $350 that only has about 15% lower performance on average in standard gaming.
As for Nvidia enabling adaptive sync support, ive owned both Freesync & Gsync monitors. One thing that is always funny to me is when people say that Freesync isnt quality controlled & that Freesync is terrible compared to Gsync
Freesync is a free technology that manufacturers can enable & the performance thereof is dependant on the quality of the manufacturing process of the monitor in question.....not freesync technology.
You will find good & bad freesync monitors at the lower end of the budget spectrum - it depends on the quality of the monitor. However, Freesync 2 has been introduced for over a year now & is AMD's official certification process for high end Freesync monitors (Nvidia fanboys never mention this & frankly I dont even think they know). A high end Freesync 2 monitor will blow your socks off with its performance theres no question about that.
Gsync is very similar to freesync 2 & in my own experience I couldnt really tell much of a difference. This is very likely due to me having had high end Freesync & gsync monitors. (There are some youtube videos where gamers were playing on Freesync 2 vs Gsync monitors & they couldnt tell the difference, there are other videos where gamers actually preferred Freesync 2, of course there are those that show G sync being preferred) - at the high end these technologies are extremely similar.
Its quite funny that the monitors Nvidia have certified as G sync approved are in fact Freesync 2 monitors & that should tell you all you need to know
Given a choice between Vega 64 & 2070 I would probably go with the 2070 simply because its a more user friendly plug & play card, and youll be covered if & when RTX technologies become more mainstream - we dont know how good the technology will be in a year from now.
If you just want to be a badass then get the Vega, throw caution to the wind & mod the crap out of it. (You can watch Gamers Nexus videos about Vega modding, sub to the vega modding reditt etc. This is a link of a recent Vega 64 vs 2070 to give you a rough benchmark of how the cards stack up out of the box)
https://youtu.be/gLgBHo-N1rA
All the best