Fabinho and Ndidi aren't better than Rice. Both of those players are excellent in a positional sense. They're very good at winning the ball back and giving it to other players that do the creating. Rice can do the job on exactly the same level as them. He is better than both at ball carrying and bringing the ball up the field. Rodri and Jorginho are definitely better on the ball and playing it through the lines. They're also extremely press resistant. Rarely losing the ball when pressed.
Ndidi was bought as a 20 year old and went to Leciester. They will never pay the prices that we have to. The other three were still expensive signings, but obviously not near to what Rice would cost. Rodri cost City £62m. Jorginho was around £51m. Fabinho was £40m. Rice will cost more, due to being PL proven, and playing for a club that doesn't need the money. He's not worth £100m in reality, but he is in West Ham's eyes.
If we bought Rice, we would need another midfielder that is better at doing the creating. I'm with you that if you spend £100m on a midfielder, you would want one of the best midfielders in the world that can do almost everything. You would want him to be able to set the tempo of the game, while also being positionally sound, and energetic enough to get around the field when needed.