I have played lots of RT games on 2080Ti and 3090. A 3090 or 4070Super can get good level of RT (RT GI, reflection and AO) + good FPS in all RT games today (PT is reserved for 4090 class and above i guess).
As for what is considered good FPS, i believe most people would be happy with 80FPS
I mean sure, but most of the reviews quote 4070 Super and the others around 60 FPS average at 1440p with settings cranked. That is definitely playable, but not what is generally strived for anymore especially in situations where people are spending alot on their setups (I mean, all those GPU's MSRP are 600+) which probably means the monitor being used is going to be something decent (Like 144hz 1440p, or a 240+ 1080p, maybe even a 120hz 2160p). Normally I would rather turn settings down to get 100hz and beyond in this day and age. Not saying 80hz is not good, you are correct, just saying when your losing over 140FPS down to 80FPS is noticeable.
Maybe both next generations will change my mind, I am more than happy to be wrong and ray tracing becomes a staple in this form. Or it may get changed to a different form and handled a different way in the future. I am just not 100% convinced at the moment of it being as necessary as its made out to be because of the trade offs.