due to the demand and limited supply currently available, any of the above that you can actually get your hands on for a reasonable price will be a good option.
even used GTX 1000 & RTX 2000 series cards are going for very high prices right now.
RX 6000 & RTX 3000 series cards are almost unobtainable at anywhere near MSRP to most.
the RTX 3070 is on par with the RX 6700 XT and i can say that i am not impressed with the performance of the RX 6700 XT compared to my previous GTX 1080 Ti. also the AMD Adrenaline 2020 software is a disappointment compared to Nvidia Control Panel.
but it's only a temporary card until something better actually becomes available for a sane price.
i have been on the hunt for a 3090 for many months now with no luck.
if you're considering putting out the money for an RX 6800 XT, MSRP on the low end ~$700 \ on the high end ~$1200;
i would definitely be looking for an RTX 3080 instead.
if you're concerned about lack of VRAM, just check what any games you're currently playing are using and compare.
Cyberpunk 2077 @ 3440x1440 with mostly ultra settings is still only using ~8GB for me and that's one of the highest reaching out of all of mine currently.