I'm running a G1 ( same resolution as the G2 ) quite happily on my 1080Ti and have no inclination for a faster GPU.I have the Rift, Rift S, Valve Index, Quest 2, and G2. For me the G2 is the best but I would only recommend the G2 to someone as their 2nd HMD not their first experience. It's not as easy to use as other HMDs. Also, you need a 3080 or better for the G2 otherwise you need to drop the resolution by the resolution is the whole point of the G2.
So many people like the Quest 2 but I cannot get mine to produce a better image than even my Rift S. The Quest 2 with link cable or air link just doesn't have enough bandwidth to compete with wired HMDs. You end up with a compressed image that doesn't perform well because it has the extra overhead of compressing and uncompressing.
Best is G2 but only if you have a 3080 or better
#2 is the Index but it's expensive
#3 is the Rift S
#4 Quest 2 if you don't care about image quality and prefer wireless play.
Conversely there are probably others who're unhappy if FPS drops below 90 - but no, you don't 'need' a 3080 for a G2 and, for me personally, it's not worth the money over my card.