RJ has stated over 200 kW sustained, and it is impossible to infer voltage from kW. 150 kW @ 400V is indistinguishable from 150 kW @ 450V, 800V or 920V.
Fair enough, I am going by what Rivian is saying on their support website
Level 3: Fast-charging — the quickest charge available. At the Rivian Adventure Network, you can charge up to 140 miles in 20 minutes.
I guess they didn't specify what RAN would be and if the car can handle more or not than what RAN can provide. I am really looking for Porsche Taycan Levels of Charging. Even though RJ said it, I will probably make that my determining factor for the vehicle as a Whole as it is key to me because I plan on taking a LOT of road trips.