I know from first-hand experience that a 2070 Super is sufficient for most games. For simulations such as DCS etc., however, it becomes unplayable. Probably a minimum of a 2080ti is needed there.
I hardly think a 1080 will do anymore, the glasses have more resolution than 4K and can do 75fps.... Pre-ordered the glasses and expect to have to upgrade my 1080ti to 3070 or similar.
This depends primarily on the type of game and how well it has been technically implemented. If you want to play the new Microsoft Flight Simulator 2020, you might even need an RTX 3090 for it to run optimally. For other games, a 1080ti is probably enough if you're not playing with the highest graphics quality. If you're willing to spend money and want optimal quality, then you'd have to aim for an RTX 3080. The RTX 3090 is completely overpriced and offers little additional performance for the price. With the new 30-series graphics cards, however, it's better to wait a few months until the market has settled in.
It should also work for people who wear glasses, as long as the glasses are not too big. You can also have special lenses made for the headset so that it works without glasses. It also matters whether it is short-sightedness or long-sightedness. The best thing is to try it out.