I changed to NRFTs on my 330d coupe prior to buying the Z4 and have to say the ride was much better. I manage motor claims for a large insurer and would recommend you tell your insurer if you change - most will not increase your premium.
If you are with a reputable insurer and you have an accident not involving a blow out, your claim is unlikely to be affected ( if you do have a blow out with NRFTs and you've not told your insurer, your claim is almost certain to be affected or turned down )
If you are with a less reputable insurer and youve not told them about the NRFTs, your claim may be affected even if the claim is nothing to do with the tyres as you have technically modified your car and not declared it - something you are required to do as part of the contract you have with your insurer