Just throwing ideas out there after my first attempt at playing WRC 10 on a CSW2.5, and XBOX Series X. I've got a classic V2 wheel on (350mm dia) so worth considering if the settings below are too heavy for anyone on a smaller wheel; you'll just need to drop the FF a little bit.
I found the base settings (named 'Fanatec Racing Wheel' in the game) to be horrible, pretty much broken. it nearly shook my seat apart with the over cooked vibrations that just seem like simple 'buzzing', that increase with vehicle speed, engine revs and tyre slip. It can be fixed though, so I wouldn't recommend racing off to refund the game straight away!
So after an hour or two of playing I came up with the following settings:
CSW2.5 WHEELBASE: SEN 900, FF 65, DRI OFF, FEI 50.
WRC GAME: Max Wheel Angle 540 (default), Force and Effects all 100 (the default), Overall Vibration <10 to taste (currently at 5 for me), with all sub-elements of vibration left at 100.
This resulted in a nice smooth drivable car, without the horrible noise/vibration but still a little bit of something/road noise in the background. Admittedly I haven't looked into the details of which vibration sub-elements would be more useful than others yet, and this will be my next step.
Given how new the game is, and some reports of people returning it already, I hope this helps. Also would be very interested to see if anyone else has some recommendations to improve it.